Induced power transmission circuit

ABSTRACT

To provide an induced power transmission circuit that transmits, from a transmission antenna ( 1 ) connected to a power supply circuit, an AC power having an angular frequency ω to a spaced reception antenna ( 2 ) with an excellent efficiency, thereby transmitting it to a load circuit. The induced power transmission circuit comprises a circuit the two ends of which are coupled by a capacitor (C 1 ) and in which the power supply circuit is connected in series to a midway port ( 1 ) (P 1 ) of the transmission antenna ( 1 ) having an effective self-inductance L 1 ; and a circuit the two ends of which are coupled by a capacitor (C 2 ) and in which the load circuit is connected in series to a midway port ( 2 ) (P 2 ) of the reception antenna ( 2 ) having an effective self-inductance L 2 ; wherein for a coupling coefficient k of the electromagnetic induction between the antennas and for a phase angle β having an arbitrary value, the angular frequency ω is set to the square root of the reciprocal of a value of L 2 ×C 2 ×(1+k*cos (β)), the output impedance of the power supply circuit is set to approximately kωL 1 *sin (β), and the input impedance of the load circuit is set to approximately kωL 2 *sin (β). There is also provided an impedance converting circuit that converts the circuit impedances.

TECHNICAL FIELD

This invention concerns the inductive electric power transfer circuit inwhich the electric power is transferred through air space with wirelessinducting means.

BACKGROUND

In patent document 1, an inductive electric power transfer circuit foran electric vehicle is proposed. That transfers electric power from aprimary winding of a power supply facility to a secondary winding of apowered device of an electrical vehicle. Since it has no contact points,the inductive electric power transfer circuit has an advantage that isfree from lose contact problems for electric terminals. The inductiveelectric power transfer circuit transfers power by electromagneticinduction on the secondary winding of the powered device withelectromagnetic field generated by current on the primary winding of thepower supply facility. A capacitor is connected between both ends of thesecondary winding, and a resonant circuit is constructed with thesecondary winding and the capacitor. The resonance of the resonantcircuit strengthens the power received by the secondary winding. Thepower is transferred to the powered device which is connected to theresonant circuit in parallel. Some applications of this kind ofinductive electric power supply circuit that transfers electric powerthrough space are toothbrushes, cellular phones, etc. The circuitaccording to patent document 1 keeps distance constant between theprimary winding and the second winding of the powered device, and thepowered devices such as toothbrushes or cellular phones are held atfixed positions in their holders to receive electric power. However,there is a deficiency that their power transfer efficiency according topatent document 1 becomes low when the distance between the primarywinding and the secondary winding is enlarged, then mutual inductances Mbetween the primary winding and the secondary winding becomes smallerthan that in closed coupled mutual inductive circuits.

Patent document 2 provides a circuit that transfers electric power froma reader/writer, which is a power supply device with a primary winding,to an IC card, which is a powered device (remote device) with asecondary winding, on condition that distance between the primarywinding and the secondary winding, which is far from the primarywinding, changes. A capacitor is connected between both ends of thesecondary winding of the powered device. The capacitor and inductance ofthe secondary winding construct a resonant circuit to increase electricpower received. The power supply device is composed of a power supplycircuit, a matching circuit, and a primary winding to adapt change ofpower transferred from the power supply device to the remote device whendistance between the primary winding and the secondary winding changes.The remote device of IC card has a variable impedance circuit which isconnected in parallel with the resonant circuit that is composed of thecapacitance and the secondary winding. The resonant circuit is connectedwith a rectifier circuit, which is connected with a load circuit of ICchip. The variable impedance is adjusted to stabilize voltage on theload circuit by detecting the voltage. The power supplied to the loadcircuit is stabilized by this circuit, but there is a problem that theelectric power supplied from the power supply circuit is uselesslyconsumed yielding low power transfer efficiency.

Patent document 3 provides a circuit which has improved power transferefficiency from a reader/writer to an IC card by using a impedancevarying means which varies two variable circuit elements, such as twovariable capacitors, or as a variable capacitor and a variableinductance, by sensing power transfer efficiency with a sensing means.

Patent document 4 provides a circuit which has improved power transferefficiency across wide space from a power supply facility to a remotedevice. The power supply facility adjusts supply of power according toinformation sent from the remote device that reports received power.That is, the electric power was supplied from the power supply to theremote device with high power transfer efficiency by varying twovariable parameters of two circuit elements, capacitor and inductor inthe power supply.

Patent document 1: WO92/017929

Patent document 2: JP10-145987

Patent document 3: JP2001-238372

Patent document 4: WO04/073166

DISCLOSURE OF THE INVENTION Problems that the Invention Tries to Solve

In patent documents 2, 3, and 4, transfer efficiencies of electric powerfrom the primary windings to the secondary windings are improved usingresonance of a resonant circuit composed of inductance of the secondarywinding and a capacitor connected between both ends of the secondarywinding of the remote device, adapting to the change of distance betweenthe primary winding and the secondary winding. A load circuit isconnected in parallel to the capacitor, which is between both ends ofthe secondary winding, to receive electric power. Patent document 3provides technology that adapts impedance of the resonant circuit byvarying two parameters of elements in the circuit in order to transferconstant electric power efficiently from a reader/writer to an IC card.However, it is not shown in patent document 3 how to vary the twocircuit element parameters in order to keep good power transferefficiency when the distance from the reader and/or writer device to ICcard is changed. It is necessary to adjust them by trial and error. Inpatent document 4 also two parameters of elements in circuit, which area capacitance and an inductance of a power supply, is adjusted by trialand error.

The first object of the present invention is to obtain the inductiveelectric power transfer circuit that transfers electric powerefficiently from the transmitter antenna, which is connected with apower supply circuit that supplies electric power, across air space tothe receiver antenna, which is connected with a load circuit thatconsumes the electric power, and adjusts parameters of elements in thecircuit without trial and error.

Circuits according to patent documents 3 and 4 have the followingproblems. That is, when the distance from the primary winding to thesecondary winding changes, two parameters, circuit elements, should beadjusted at the same time to match the impedances of the circuits inorder to adapt the change and keep high efficiency of electric powertransmission. Setting both parameters of the two elements in thecircuits properly at the same time is not easy, or impedances of thecircuits will not match. Therefore, it is the second object of thepresent invention to obtain the inductive electric power transfercircuit in which the electric power can be transferred efficiently fromthe power supply circuit to the load circuit through space by adjustingonly one parameter of element in circuit.

Means for Solving the Problems

Researching for solution of this problem, it was found that the electricpower can be efficiently transferred by reducing impedances of the powersupply circuit and the load circuit to certain specific resistances(induced resistances) on antennas. The induced resistance is calculatedby dividing voltage that is induced on the antenna by the antennacurrent. So the circuit according to the present invention can transferelectric power efficiently with matching the impedances of the powersupply circuit and the load circuit with the induced resistances on theantennas connected to them.

That is, an aspect of the present invention is an inductive electricpower transfer circuit that transfers electric power with angularfrequency ω from a transmitter antenna connected to a power supplycircuit to a receiver antenna connected to a load circuit through space.The circuit has a capacitance C1 connected between both ends of thetransmitter antenna, whose effective self-inductance is represented bythe symbol L1. The circuit has a capacitance C2 connected between bothends of the receiver antenna, whose effective self-inductance isrepresented by the symbol L2. The power supply circuit is connected inseries in the middle of the transmitter antenna. The load circuit isconnected in serried in the middle of the receiver antenna. Distancebetween the transmitter antenna and the receiver antenna is not greaterthan ½π wavelengths of electromagnetic field that carry electric power.An inductive coupling factor between the transmitter antenna and thereceiver antenna is represented by the symbol k. The angular frequency ωis set to reciprocal of square root of L2×C2×(1+k×cos (β)) on phaseangle β that is more than zero radians and less than π radians. Outputimpedance of the power supply circuit is matched to kωL1·sin (β)≡r1, andinput impedance of the load circuit is matched to kωL2·sin (β)≡r2, sothat power is transferred efficiently from the power supply circuit tothe load circuit.

The effective self-inductances of the antennas in theinductive-electric-power-transfer-circuit according to the presentinvention change according to electric current distribution on theantennas. Basic effective self-inductance among them is theself-inductance L that has electric current with uniform distribution onthe antenna. Inductive coupling factor k can be calculated, or obtainedfrom electromagnetic field simulation as follows. That is, inductivecoupling factor k is obtained as k=r/(ω)L), where the induced resistancer is obtained from simulation of the third type resonance of theprinciple of the present invention. The inductive coupling factor k isindependent from electric current distribution of antenna and is almostconstant. Effective self-inductance L of the antenna that has electriccurrent with non-uniform distribution can be calculated as L=r/(ωk),where the inductive coupling factor k is obtained previously. Thecapacitance C, which is total capacitance including parasiticcapacitance, can be calculated as 1/(ω²L). The angular frequency ω ofthe resonance shifts from 1/√(L2×C2) to 1/√{L2×C2×(1+k×cos (β))} in thesecond type resonance of the principle of the present invention. Theinduced resistance r1 appears on the transmitter antenna as kωL1×sin(β); and the induced resistance r2 appears on the receiver antenna askωL2×sin (β). Electric power can be transferred efficiently by matchingimpedances of the power supply circuit and the load circuit with theinduced resistances appeared on the antennas connected to them.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit, wherein the combination of the powersupply circuit and the transmitter antenna is replaced with acombination of a transmitter antenna, a first inductive coupling wiringthat inductively couples with the transmitter antenna with mutualinductance M1, a second power supply circuit that is connected betweenboth ends of the first inductive coupling wiring. Output impedance ofthe second power supply circuit is set to almost (2πf×M1)²/r1.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the combination of circuits ofthe load circuit and the receiver antenna is replaced with a combinationof a receiver antenna, a second inductive coupling wiring thatinductively couples with the receiver antenna with mutual inductance M2,a second load circuit that is connected between both ends of the secondinductive coupling wiring. Input impedance of the second load circuit isalmost (2πf×M2)²/r2.

That is, as shown in FIG. 21, the inductive electric power transfercircuit according to the present invention has an inductive couplingwiring 6 that inductively couples with the receiver antenna 2, and has aload circuit that is connected between both ends of the inductivecoupling wiring 6 at port 4 (P4). Input impedance of the load circuit isset to almost (2πf×M2)²/r2, where r2 is induced resistance on thereceiver antenna 2. On the other hand, present invention provides aninductive electric power transfer circuit which has an inductivecoupling wire 6 that is connected to the power supply circuit and isinductively coupled with the transmitter antenna. An output impedance ofthe power supply circuit is set to almost (2πf×M1)²/r1.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the combination of the powersupply circuit and the transmitter antenna and the capacitance C1 isreplaced with an antenna that receives electromagnetic wave from theair.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the combination of circuits ofthe load circuit and the receiver antenna and the capacitance C2 isreplaced with an antenna that radiates electromagnetic wave into theair.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the transmitter antennacombines with a first inductive coupling wiring. And output impedance ofthe second power supply circuit is set to almost (2πf×L1)²/r1.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the receiver antenna combineswith a second inductive coupling wiring concurrently. And inputimpedance of the second load circuit is set to almost (2πf×L2)²/r2.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit that transfers electric power withangular frequency ω from a transmitter antenna connected to a powersupply circuit to a receiver antenna connected to a load circuit throughspace. The circuit has a capacitance C1 connected between both ends ofthe transmitter antenna, whose effective self-inductance is representedby the symbol L1. The circuit has a capacitance C2 connected betweenboth ends of the receiver antenna, whose effective self-inductance isrepresented by the symbol L2. The power supply circuit is connected inseries in the middle of the transmitter antenna. The load circuit isconnected in serried in the middle of the receiver antenna. Distancebetween the transmitter antenna and the receiver antenna is not greaterthan ½π wavelengths of electromagnetic field that carry electric power.Mutual inductance between the transmitter antenna and the receiverantenna is represented by the symbol M. The angular frequency ω is setto reciprocal of square root of L2×C2. Input impedance of the loadcircuit is set to (ωM)²/Z1, where Z1 represents output impedance of thepower supply circuit.

That is, the inductive electric power transfer circuit according to thefirst type resonance of the present invention with angular frequency ωof 1/√(L2×C2) converts the output impedance Z1 to the input impedanceZ2=(ωM)²/Z1.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the combination of the powersupply circuit and the transmitter antenna is replaced with acombination of a transmitter antenna, a first inductive coupling wiringthat inductively couples with the transmitter antenna with mutualinductance M1, a second power supply circuit that is connected betweenboth ends of the first inductive coupling wiring. Input impedance of theload circuit is set to almost (M1/M1)²Z3, where Z3 represents outputimpedance of the second power supply circuit.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the combination of circuits ofthe load circuit and the receiver antenna is replaced with a combinationof a receiver antenna, a second inductive coupling wiring thatinductively couples with the receiver antenna with mutual inductance M2,a second load circuit that is connected between both ends of the secondinductive coupling wiring. Input impedance of the second load circuit isalmost (M2/M1)²Z1, where Z1 represents output impedance of the powersupply circuit.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the transmitter antennacombines with a first inductive coupling wiring. And input impedance ofthe load circuit is set to almost (M/L1)²Z3, where Z3 represents outputimpedance of the second power supply circuit.

An aspect in accordance with the present invention provides an inductiveelectric power transfer circuit; wherein the receiver antenna combineswith a second inductive coupling wiring concurrently. And inputimpedance of the second load circuit is set to almost (L2/M)²Z1, whereZ1 represents output impedance of the power supply circuit.

Effects of the Invention

The inductive electric power transfer circuit according to presentinvention transfers electric power at the angular frequency ω from thetransmitter antenna, which is connected to the power supply circuit, tothe receiver antenna through space. Power is transferred efficientlyfrom the power supply circuit to the load circuit by decreasing theimpedances of the power supply circuit and the load circuit to match theinduced resistances on the antennas. The induced resistances are easilycalculated according to present invention. The inductive electric powertransfer circuit transfers power in full efficiency from the powersupply circuit to the load circuit. Moreover, an impedance converterthat freely converts impedances can be constructed with air-core coil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view and side view showing the transmitter antenna andthe receiver antenna of a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing the inductive electric powertransfer circuit of the present invention.

FIG. 3 is a graph for S parameter (S21) for the power transfer accordingto the first embodiment of the present invention.

FIG. 4 is a graph for induced resistance (r) as a function of spacing hbetween antennas according to the first embodiment of the presentinvention.

FIG. 5 is a graph for S parameter (S21) for power transfer according tomodification 1 of the first embodiment of the present invention.

FIG. 6 is a graph for induced resistance (r) as a function of spacing hbetween antennas according to a modification 1 of the first embodimentof the present invention.

FIG. 7 is a plan view and side view showing the transmitter antenna andthe receiver antenna of a modification 2 of the first embodiment of thepresent invention.

FIG. 8 is a graph for induced resistance (r) as a function of spacing hbetween antennas according to the modification 2 of the first embodimentof the present invention.

FIG. 9 is a graph for power transfer efficiency as a function of spacingh between antennas according to the modification 2 of the firstembodiment of the present invention.

FIG. 10 is a graph for induced resistance (r) as a function of spacing hbetween antennas according to a modification 3 of the first embodimentof the present invention.

FIG. 11 is a graph for induced resistance (r) as a function of shiftingdistance d between antennas according to a modification 4 of the firstembodiment of the present invention.

FIG. 12 is a graph for power transfer efficiency as a function ofshifting distance d between antennas according to the modification 4 ofthe first embodiment of the present invention.

FIG. 13 is a graph for power transfer efficiency as a function ofimpedance Z of a power supply circuit and a load circuit according to asecond embodiment of the present invention.

FIG. 14 is a plan view and side view showing a transmitter antenna and areceiver antenna according to a third embodiment of the presentinvention.

FIG. 15A is a graph for induced resistance (r) as a function of spacingh between antennas according to the third embodiment of the presentinvention.

FIG. 15B is a graph for power transfer efficiency as a function ofspacing h between antennas according to the third embodiment of thepresent invention.

FIG. 16A is a graph for induced resistance (r) as a function of spacingh between antennas according to a modification 5 of the third embodimentof the present invention.

FIG. 16B is a graph for power transfer efficiency as a function ofspacing h between antennas according to the modification 5 of the thirdembodiment of the present invention.

FIG. 17A is a graph for induced resistance (r) as a function of spacingh between antennas according to a fourth embodiment of the presentinvention.

FIG. 17B is a graph for power transfer efficiency as a function ofspacing h between antennas according to the fourth embodiment of thepresent invention.

FIG. 18 is a plan view and side view showing a transmitter antenna and areceiver antenna according to a sixth embodiment of the presentinvention.

FIG. 19A is a graph for induced resistance (r) as a function of spacingh between antennas according to the sixth embodiment of the presentinvention.

FIG. 19B is a graph for power transfer efficiency as a function ofspacing h between antennas according to the sixth embodiment of thepresent invention.

FIG. 20A is a plan view and side view showing a transmitter antenna anda receiver antenna according to an eighth embodiment of the presentinvention.

FIG. 20B is a graph for S parameter (S21) of power transfer according tothe eighth embodiment of the present invention.

FIG. 21A is a plan view and side view showing a transmitter antenna anda receiver antenna according to a ninth embodiment of the presentinvention.

FIG. 21B is a graph for S parameter (S21) of power transfer according tothe ninth embodiment of the present invention.

FIG. 22A illustrates a plan view of a transmitter antenna and a receiverantenna according to present invention.

FIG. 22B illustrates a plan view of a transformer according to aneleventh embodiment of the present invention.

FIG. 23A is a plan view of the transmitter antenna and the receiverantenna according to a twelfth embodiment of the present invention.

FIG. 23B is a graph for S parameter (S21) of power transfer according tothe twelfth embodiment of the present invention.

FIG. 24A is a plan view of a transmitter antenna and a receiver antennaaccording to a thirteenth embodiment of the present invention.

FIG. 24B is a graph for S parameter (S21) of power transfer according tothe thirteenth embodiment of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

-   1: Transmitter antenna-   2: Receiver antenna-   3: Power supply circuit-   3 a, 3 b, 3 c: Transmitter circuit-   4: Load circuit-   4 a, 4 b, 4 c: Receiver circuit-   5: Impedance converter-   6: Inductive coupling wiring-   C1, C2: Capacitance-   d: Shifting distance-   D, G: Coil diameter-   : Frequency-   ω: Angular frequency-   h: Antenna spacing-   I1, I2: Antenna current-   L, L1, L2: Effective self-inductance-   M, Mo, M1, M2: Mutual inductance-   min: Parasitic capacitance-   Pe: Power transfer efficiency-   P1: Port 1 (joining terminal)-   P2: Port 2 (joining terminal)-   P3: Port 3 (joining terminal)-   P4: Port 4 (joining terminal)-   P5: Port 5 (joining terminal)-   P6: port 6 (joining terminal)-   r, r1, r2, r3: Induced resistance-   y: Real number-   X, Y: Axis of coordinate-   Z1, Z2, Z3, Z4, Z5: Impedance

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Principle of PresentInvention>

FIG. 1A shows the plan view (XY-plane) of a transmitter antenna 1 and areceiver antenna 2 of an inductive electric power transfer circuitaccording to present invention. And FIG. 1B shows the side view of them.The inductive electric power transfer circuit according to presentinvention has a resonance circuit which has the transmitter antenna 1 ofcoiled wiring, which has effective self-inductance L1, both ends of thatare connected to a capacitance C1. A power supply circuit 3 is connectedto port 1 (P1) in series, which is at the middle of the transmitterantenna 1. Similarly, the inductive electric power transfer circuit hasa resonant circuit which has the receiver antenna 2 of coiled wiring,which has effective self-inductance L2, whose both ends are connected toa capacitance C2. And the load circuit 4 is connected to port 2 (P2) inseries, which is at the middle of the receiver antenna 2. As shown inFIGS. 1 a and 1 b, both antennas that couple by electromagneticinduction are set within near-field region of (½π) wavelength ofresonant electromagnetic field on the antennas. When both antennas areset within the near-field region, effect of interaction of theelectromagnetic induction is greater than effect of radiation. Mutualinductance M between both antennas usually become below 60% of√/(L1×L2), which is mutual inductance of them in close coupling, whenthe transmitter antenna 1 and the receiver antenna 2 are separated.

In FIG. 1, the coiled wiring of the transmitter antenna 1 and thereceiver antenna 2 are parallel in two levels that is parallel toXY-plane. The axes of the coiled wirings of the transmitter antenna 1and the receiver antenna 2 are overlapped; and the antennas are setclose in the direction of the axis. Placement of the antennas is notrestricted to the case; they can be set in other placements where theyare within the near-field distance that is (½π) wavelength of resonantelectromagnetic field on the antennas. As shown in FIG. 20 a, theantennas can be set in coplanar. For each antenna, both ends of theantenna are connected to capacitance, and the shape of the antenna isone or several turned spiral or coiled wiring. The capacitances of C1and C2, which connect both ends of the antennas, can be only parasiticcapacitances without external capacitors between both ends of theantenna. Shape and size of the transmitter antenna 1 and the receiverantenna 2 is not necessarily the same. Shape of the transmitter antenna1 and the receiver antenna 2 is not necessarily coil in FIG. 1. Forinstance, a dipole antenna for transmitter antenna 1 in FIG. 24A canresonate to transfer power in full efficiency Pe, which is defined byEquation 29 described hereinafter.

The inductive electric power transfer circuit according to presentinvention is modeled by the circuit in FIG. 2A. The circuit has mutualinductance M between the transmitter antenna 1 that has effectiveself-inductance L1 and the receiver antenna 2 that has effectiveself-inductance L2. The inductive electric power transfer circuitsupplies the power from the power supply circuit 3, which is connectedto transmitter antenna 1, to the load circuit 4, which is connected toreceiver antenna 2, through space. Capacitance C1, which is connected toboth ends of the transmitter antenna 1, can be composed of a capacitorin the tank circuit in which power supply circuit 3 supplies electriccurrent with angular frequency ω to the transmitter antenna 1. When thecapacitance C1, which is connected to both ends of the antenna wiring,is greater than the parasitic capacitance, the position of the terminalof port 1 (P1), at which the power supply circuit 3 is connected inseries, on the transmitter antenna 1 can be at a connecting point of oneend of the antenna wiring and the capacitance C1. When the capacitanceC2, which is connected to both ends of the antenna wiring, is greaterthan the parasitic capacitance, the position of the terminal of port 2(P2), at which the load circuit 4 is connected in series, on thereceiver antenna 2 can be at the point which connect one end of theantenna wiring and the capacitance C2.

The following were found as a result of the research, and it providedpresent invention. When an inductive electric power transfer circuit iscomposed of the above-mentioned circuit structure, it is possible toresonate the receiver circuit 4 a, which is a resonant circuit composedof the receiver antenna 2 and the capacitance C2, and the transmittercircuit 3 a, which is a resonant circuit composed of the transmitterantenna 1 and the capacitance C1. When following requirements arefulfilled, the power can be transferred from the power supply circuit 3to the load circuit 4 in full efficiency. The conditions in which powercan be transferred efficiently are described as follows. At port 1 (P1)in FIG. 2A, where the power supply circuit 3 connects to the transmitterantenna circuit 1, Voltage Ein is as following Equation (1).

(Equation 1)

Ein=j{ωL1−(1/(ωC1))}×I1+jωM×I2

where I1 is an antenna current that is on the transmitter antenna 1, I2is an antenna current that is on the receiver antenna 2, ω=2πf isangular frequency, and f is frequency of the currents. FollowingEquation 2 shows a function of input impedance Zin of the transmitterantenna circuit 1 seen from the power supply circuit 3 at port 1 (P1) inFIG. 2A.

(Equation 2)

Ein=Zin×I1

The last term (jωM×I2) in the right side of Equation 1 is described asEquation 3 for an induced voltage E1 on the transmitter antenna 1; thevoltage E1 is induced by changing electromagnetic field near the wiringof transmitter antenna 1, field which is caused by high-frequencycurrent I2 on the receiver antenna 2.

(Equation 3)

E1=jωM×I2

Equation 1, 2, and 3 yield the following Equation 4 for input impedanceZin of the antenna circuit.

(Equation 4)

Zin=j{ωL1−(1/ωC1))}+E1/I1

The input impedance Zin is a sum of impedances of components in thecircuit and pseudo impedance (E1/I1) added by the induced voltage E1.

And Zin has a real part inherited from the added impedance (E1/I1). Thereal part of Zin is defined as induced resistance r1 in the followingEquation 5.

(Equation 5)

r1≡Real(E1/I1)=Real(jωM×I2/I1)

Induced resistance r1 is shown in the following Equation 7, where ratioof the current I2 of the receiver antenna 2 to the current I1 of thetransmitter antenna 1 is shown in Equation 6 which uses parameters ofreal number that are an electric current ratio parameter α and a phaseangle β.

(Equation 6)

I2/I1≡α·exp(−jβ)

(Equation 7)

r1=β·ωM·sin (β)

Power is most efficiently transferred from a power supply circuit 3 to atransmitter antenna 1 when the impedance Z1, which is the impedance ofthe power supply circuit 3, matches (equal) with the impedance Zin,which is the impedance of the transmitter antenna 1 looking from thepower supply circuit 3 at Port 1 (P1) in FIG. 2A. When output impedanceZ1 of power supply circuit 3 is resistance without reactance, thecondition of matching is that Z1 is equal to the induced resistance r1.The induced resistance r1 is calculated dividing a component of theinduced voltage E1 that is in phase with current I1 on the transmitterantenna by the current I1.

Induced voltage E2 is induced on the receiver antenna 2 by the antennacurrent I1 on the transmitter antenna 1. The induced voltage E2 is shownin Equation 8.

(Equation 8)

E2=jωM×I1

A voltage Eout at port 2 (P2), at which the receiver antenna 2 isconnected with the load circuit 4, is shown in the following Equations 9and 10.

(Equation 9)

Eout=E2+j{ωL2−(1/(ωC2))}×I2

(Equation 10)

Eout=−Z2×I2

Induced resistance r2 is defined by real part of output impedance frominduced voltage E2, that yields following Equation 11 for inducedresistance r2.

(Equation 11)

r2≡Real(E2/(−I2))

=Real(−jωM×I1/I2)=(1/α)·ωM·sin (β)

Power transfers most efficiently from the receiver antenna 2 to the loadcircuit 4 when the output impedance (−E2/I2), where the induced voltageE2 on the receiver antenna 2 works as supplied power, is matched withthe sum of the input impedance Z2 and a reactance of the receiverantenna 2 j{ωL1−(1/(ωC1))}. Thereby, when input impedance Z2 of the loadcircuit 4 has no reactance, the matching condition is that Z2 is equalto the induced resistance r2. The induced resistance r2 is calculated bydividing the component of the voltage E2 that is in phase with thecurrent I2 by the current I2, where E2 is an induced voltage on thereceiver antenna 2 by the current I1 on the transmitter antenna 1, I2 isa current on the receiver antenna 2.

Present invention can compose a receiver circuit 4 b that is shown inthe right part of FIG. 2B, which is series of a receiver antenna 2 and aprimary winding of a transformer, and in which both ends of thesecondary winding of the transformer are connected with a load circuit 4at Port 4 (P4). The receiver circuit 4 b in the right part of FIG. 2B isequivalent to the receiver circuit 4 a in the right part of FIG. 2( a)in the condition where angular frequency ω is fixed. The circuit shownin FIG. 21A is one embodiment of the receiver circuit 4 b in the rightpart of FIG. 2B that has a transformer, which connects a receiverantenna 2 with a load circuit 4. The receiver circuit in FIG. 21A has areceiver antenna 2 that is coiled (spiral) that combines with theprimary winding of the transformer. And the receiver circuit has ainductive coupling wiring 6 that is coiled or spiral, which is thesecondary winding of the transformer, which is placed close to thereceiver antenna 2 and is in a level parallel to the level (XY-plane) ofthe receiver antenna 2. The circuit shown in FIG. 21A has a transmittercircuit 3 a in the left part of FIG. 2A, where the power supply circuit3 is connected in series at port 1 (P1) in the middle of the transmitterantenna 1 whose both ends are connected to the capacitance C1. Thereceiver circuit 4 b in the right part of FIG. 2B has an inductivecoupling wiring 6 that inductively couples with the receiver antenna 2by mutual inductance M2; both ends of the inductive coupling wiring 6are connected to a load circuit 4 at port 4 (P4). In the circuit in FIG.21( a), self-inductance of inductive coupling wiring 6 is small comparedto the induced resistance r2, so that the induced resistance (impedanceof the inductive coupling wiring 6) looking from the load circuit 4 atport 4(P4) is (2πf×M2)²/r2. Another embodiment for the circuit can becomposed where the circuit of the transmitter antenna 1 is replaced witha transmitter circuit 3 b in the left of FIG. 2 b, which has aninductive coupling wiring 6.

Moreover, the circuit in FIG. 21( a) can be replaced with a circuit inwhich the receiver antenna 2 combines with the inductive coupling wiring6 that constructs a receiver circuit 4 c in the right of FIG. 2C. In thereceiver circuit 4 c, port 6 (P6) that is a combination of both ends ofthe receiver antenna 2 combines with port 4 (P4), which is connected toload circuit 4. At port 6 (P6), load circuit 4 and the capacitance C2are connected in parallel. The induced resistance (impedance) at Port 6looking from the load circuit 4 is (ω×L2)²/r2. That is, in the receivercircuit 4 c in FIG. 2C, the mutual inductance M2 of the inductivecoupling wiring 6 in the receiver circuit 4 b in FIG. 2B is replacedwith the effective self-inductance L2 of the receiver antenna 2. Thecircuit of the transmitter antenna 1 can be replaced with thetransmitter circuit 3 b in the left of FIG. 2B, where port 3 (P5) thatis a combination of both ends of the inductive coupling wiring 6 isconnected to the power supply circuit 3. Moreover, the transmittercircuit 3 b can be replaced with the transmitter circuit 3 c in the leftof FIG. 2C, where port 5 (P5) that is a combination of both ends of thetransmitter antenna 1 is connected to the power supply circuit 3.

An inductive electric power transfer circuit in FIG. 24A is composed ofa receiver antenna 2 that is a coiled (spiral) antenna wiring, atransmitter antenna 1 that is a dipole antenna, which receives theelectromagnetic wave from the air, working for the function of the powersupply circuit 3. In the circuit, the dipole antenna receives power ofelectromagnetic wave from the air and causes electric current on it. Theelectric current generates induced voltage on the receiver antenna 2.Thus, the dipole antenna has both functions for power supply circuit 3and transmitter antenna 1. The induced voltage generates inducedresistance r2 on the receiver antenna 2. Power of electromagnetic wavecan be received efficiently from the air when the induced resistance r2is matched to input impedance Z2 of the load circuit 4. Similarly, aninductive electric power transfer circuits is composed of a transmitterantenna 1 that is a coiled (spiral), the receiver antenna 2 that is adipole antenna and works for radiating electromagnetic wave and consumesthe power. That is, the dipole antenna has functions for receiverantenna 2 and load circuit 4. Electromagnetic wave can be efficientlyradiated by matching induced resistance r2 of the receiver antenna 2with the radiation resistance of the dipole antenna that is inputimpedance Z2 of load circuit 4.

In the following, cases where impedances are matched in an inductiveelectric power transfer circuit in FIG. 2A are analyzed in detail, andangular frequencies ω that cause resonance are analyzed in detail. Inthe case when output impedance Z1 of the power supply circuit 3 ismatched with the induced resistance r1 and input impedance Z2 of theload circuit 4 is matched with the induced resistance r2, Equations 1and 9 yield the following Equations 12 and 13.

(Equation 12)

ωL1−(1/(ωC1))=−α·ωM·cos (β)

(Equation 13)

ωL2−(1/(ωC2))=−(1/α)·ωM·cos (β)

Electromagnetic field on the transmitter antenna 1 and the receiverantenna 2 resonate when Z1=r1 and Z2=r2 and Equations 12 and 13 aresatisfied, so that electric power is transferred from the power supplycircuit 3 to the load circuit 4 in full efficiency.

In this case, when cos (β) is not zero, Equations 7, 11, 12, and 13yield the following Equations.

(Equation 14)

r1·r2=(ωM)² −g1×g2

(Equation 15)

g1≡ωL1−(1/(ωC1))

(Equation 16)

g2≡ωL2−(1/(ωC2))

(Equation 17)

α² =g1/g2

(Equation 18)

sin (β)² =Z1·Z2/(ωM)²

When M, L1, C1, L2, and C2 are decided, r1×r2 is given by Equation 14 asa function of ω. And, an electric current ratio parameter α is given byEquation 17. Next, the phase angle β is given by Equation 18. Next, r1and r2 are given by Equation 7 and Equation 11. Especially, g1×g2 ispositive according to Equation 17. The condition where Equation 14 issatisfied when ωM is small is as follows. That is, a certain value of ωshould exist which is represented by symbol ωo that satisfies g1=g2=0.The condition for that is the following Equation 19.

(Equation 19)

L1·C1=L2·C2≡(1/ωo)²

(First Type Resonance)

In the condition where Equation 19 is satisfied, when ω is ωo, Equations12 and 13 yield that cos (β) is zero, sin (β) is one, and g1=g2=0. Thisis named “first type resonance,” which will be described later.

(Second Type Resonance)

In the condition where Equation 19 is satisfied, when ω is not ωo,Equations 6, 7, 11, and 15 to 17 yield the following Equation 20. Thisis named “second type resonance”.

(Equation 20)

|I2/I1|²=α² =L1/L2=C2/C1=r1/r2

Equation 20 yields the following Equation 21.

(Equation 21)

L1×|I1|² =L2×|I2|²

This Equation 21 shows that energy of electromagnetic field on thetransmitter antenna 1 is equal to energy of electromagnetic field on thereceiver antenna 2, and both antennas mutually exchange the energy ofthe electromagnetic fields and resonate. This Equation 21 yields thefollowing Equation 22.

(Equation 22)

|I2|=|I1|×√(L1/L2)

That is, in the resonance, the ratio of the electric current I1 of thetransmitter antenna 1 to the electric current I2 of the receiver antenna2 is the square root of the ratio of the effective self-inductance L2 ofthe receiver antenna 2 to the effective self-inductance L1 of thetransmitter antenna 1. Equation 22 is satisfied also in anelectromagnetic field simulation on the antenna circuits that resonateand has good efficiency (in the efficiency of almost 100%) in energytransfer between the antennas. Since great electric current flows onreceiver antenna 2 as shown in Equation 22, high frequent antennacurrent I2 on the receiver antenna 2 causes change of electromagneticfield, so that it causes induced voltage E1 on the transmitter antenna1.

In the condition where Equation 19 is satisfied, Equations 7, 11, 12,and 13 yield Equations from 24 through 27 that are with inductivecoupling factor k, which is defined by Equation 23.

(Equation 23)

K≡M/√(L1×L2)

(Equation 24)

R1=kωL1·sin (β)

(Equation 25)

R2=kωL2·sin (β)

(Equation 26)

ωL1−1/(ωC1)=−kωL1·cos (β)

(Equation 27)

ωL2−1/(ωC2)=−kωL2·cos (β)

Equation 26 and 27 yield the following Equation 28.

(Equation 28)

ω=ωo/√(1+k·cos (β))

The above-mentioned relations can be described as follows.

That is, the antenna system that satisfies Equation of L1×C1=L2×C2=1/ωo2can transfer electric power in full efficiency when: angular frequency ωof the current that transfers power is the reciprocal of the square rootof L1×C1×(1+k×cos (β)), where phase angle β is from zero to π radian;output impedance Z1 of the power supply circuit 3, which is connected inseries with the transmitter antenna 1 at port 1 (P1), is r1=kωL1×sin(β). input impedance Z2 of the load circuit 4, which is connected inseries with the receiver antenna at port 2 (P2), is r2=kωL2·sin (β).There are upper limits for the induced resistances r with which thepower can be transferred from the power supply circuit 3 to the loadcircuit 4 in full efficiency. The upper limits of the inducedresistances r with which electric power can be transferred rises whenthe induced coupling factor k rises by approximating the air-coredreceiver antenna 2 to the facing air-cored transmitter antenna 1. Upperlimit of the induced resistance r1 is kωL1. Upper limit of the inducedresistance r2 is kωL2. Power can be transferred in full efficiency whenoutput impedance Z1 of the power supply circuit 3 is set to the inducedresistance r1 that is less than the upper limit, and input impedance Z2of the load circuit 4 is set to the induced resistance r2 that is lessthan the upper limit. When output impedance Z1 of power supply circuit 3and input impedance Z2 of load circuit 4 are set smaller than the upperlimits of the induced resistances, those impedances can be equal to thecorresponding induced resistances by adjusting sin (β), which is lessthan one, in Equations 24 and 25, so that the impedances match totransfer electric power. In that case, cos (β) is not zero, so that thetransmitter antenna 1 and the receiver antenna 2 resonate at angularfrequency ω that is shifted from ωo according to Equation 28.

By applying the second type resonance, an inductive electric powertransfer circuit can be composed; the circuit can keep constantimpedances of the power supply circuit 3 and the load circuit 4 thatmatch with induced resistances r1 and r2 although arrangement of thetransmitter antenna 1 and the receiver antenna 2 is not steady and theinductive coupling factor k changes. The circuit has a power supplycircuit 3 whose output impedance Z1 is fixed and is equal to the inducedresistance r1 that is less than the upper limit. And the circuit has aload circuit 4 whose input impedance Z2 is fixed and is equal to theinduced resistance r2 that is less than the upper limit. The powersupply circuit 3 adapts to the change of the inductive coupling factor kby changing phase angle β and angular frequency ω to resonate. The powersupply circuit 3 that adjusts like that can be composed of apositive-feedback circuit that makes the resonance current oftransmitter antenna 1 positively return to power supply circuit 3, andcomposed of an amplifier that amplifies the electric current and outputsit. As a result, the power supply circuit 3 is adjusted to outputelectric current I1 that is with resonant angular frequency ω. That is,the antenna circuit can resonate by adapting for the variation of theinductive coupling factor k. The inductive electric power transfercircuit is effective to keep power transfer in full efficiency when theinductive coupling factor k varies.

Power transfer efficiency Pe of the antenna system is approximatelygiven by the following Equation 29.

(Equation 29)

Pe=(1−ref2/r2)/(1+ref1/r1))

where ref1 is effective resistance of the transmitter antenna 1, ref2effective resistance of the receiver antenna 2. Equation 29 is effectivewhen the induced resistance r2 is greater than ref2. When the effectiveresistance of the transmitter antenna 1 (ref1) is smaller than theinduced resistance r1, and the effective resistance of receiver antenna2 (ref2) is smaller than the induced resistance r2, power is transferredefficiently. When the effective resistances of the antennas (ref) aremuch less than induced resistances r, the power transfer efficiencybecomes almost 100%. The transmitter antenna 1 and the receiver antenna2 can be dipole antennas or coiled (spiral) antennas that are shown inFIG. 1. When the antennas are coiled, effective self-inductances L1 andL2 of the antennas become greater and induced resistances r1 and r2becomes greater than that of dipole antennas according to Equations 24and 25, so that power transfer efficiency Pe, which is calculated usingEquation 29, from the transmitter antenna 1 to the receiver antenna 2becomes greater than that of dipole antennas.

(Third Type Resonance)

Especially, when ω≈ωo, left sides of Equations 26 and 27 are almostzero, so that the right sides of them are almost zero, β is almost π/2radian, cos (β) is almost zero, and sin (β) is almost one. Thereby,Equations 24 and 25 reduce to the following approximate Equations 30 and31.

(Equation 30)

R1≈kωL1

(Equation 31)

R2≈kωL2

Namely, in the case of ω≈ωo, when output impedance Z1 of the powersupply circuit 3 shown in FIG. 2A is matched to induced resistance r1 inEquation 30 and input impedance Z2 of the load circuit 4 is matched toinduced resistance r2 in Equation 31, the power can be transferred infull efficiency from the power supply circuit 3 to the load circuit 4.The third type resonance is a kind of the second type resonance and akind of the first type resonance. That is, it is the second typeresonance and first type resonance. In the third type resonance, thereare relations shown in Equations 30 and 31 between induced resistancesr, inductive coupling factor k, and effective self-inductances L of theantennas. In the third type resonance, when the inductive couplingfactor k is known previously, using the Equations, the effectiveself-inductance L of the antennas can be calculated with inducedresistances r obtained by simulation. In another case, inductivecoupling factor k can be calculated from the induced resistance robtained by simulation when effective self-inductance L is knownpreviously.

(First Type Resonance)

The case of the first type resonance described before is analyzed indetail as follows. In the first type resonance, Equation 19 is satisfiedand sin (β) is one and g1=g2=0. In the case, the phase angle β, whichrepresents phase difference between antenna currents I1 and I2, is 90degrees (π/4 radian). The antenna system resonates with angularfrequency ω=ωo. And Equations 32 to 35 are satisfied.

(Equation 32)

Cos (β)=0

(Equation 33)

R1=ωM·α

(Equation 34)

R2=ωM/α

(Equation 35)

I2/I1=−jα

The relations can be described as follows. That is, in an antenna systemthat satisfies L1×C1=L2×C2=1/ωo², electric power can be transferred infull efficiency on the conditions: angular frequency ω of the currentsthat transfer electric power is set to ωo; output impedance Z1 of thepower supply circuit 3 that is connected in series with the transmitterantenna 1 is matched with r1=ωM×α, where α is a free positive number;the input impedance Z2 of load circuit 4 that is connected in serieswith the receiver antenna 1 is matched with r2=ωM/α. That is, in theresonance, the angular frequency ω=2πf agrees with ωo as shown inEquation 19, and there is a character that the antenna currents ratio αcan be set free to transfer electric power. Since the ratio α betweenthe antenna currents is free, electric power can be transferredefficiently when the current I1 on the transmitter antenna 1 is greatand great electromagnetic field is generated even if the current I2 onthe receiver antenna 2 is small. Oppositely, it means the electric powercan be transferred efficiently when the electric current I2 of thereceiver antenna 2 is great even if the electric current I1 of thetransmitter antenna 1 is small. Product of the induced resistances r1and r2 is the square of (ωM), and the product is constant. The ratiobetween the induced resistances r1 and r2 is a square of the ratio αbetween the antenna currents, and it can be changed freely.

Using the phenomenon at the first type resonance, the inductive electricpower transfer circuit can compose the impedance converter of air-corecoil that converts the induced resistance r1 of the transmitter antenna1 to the induced resistance r2 of the receiver antenna 2. That is, theimpedance converter that converts the impedance Z1 of the power supplycircuit 3 into the induced resistance r2=(ωM)²/Z1 of the load circuit 4can be composed of the circuit in FIG. 2( a).

The spacing of the transmitter antenna 1 and the receiver antenna 2 forthe impedance converter is changed, so that the coefficient of couplingk is changed and the mutual inductance M is changed. This makes itpossible to compose the impedance converter which can change only theinduced resistance r2 of the receiver antenna 2 without changing theoutput impedance Z1 of the power supply circuit 3 on the transmitterantenna. The impedance converter can change the induced resistance r2,which is converted, only by changing one parameter k. It is effective tochange the circuit parameter easily and to adjust the impedance easily.

In the following embodiments, the output impedance Z1 of the powersupply circuit 3 and the input impedance Z2 of load circuit 4 is given,which enable to transfer electric power in full efficiency from thepower supply circuit 3 to the load circuit 4, by electromagnetic fieldsimulation. The induced resistances are given by assuming the values tobe the induced resistances r1 and r2. The induced resistance r1 isωMα·sin (β), and the induced resistance r2 is ωM·sin (β)/α. In thefollowing electromagnetic field simulations, the transmitter antenna 1and receiver antenna 2 are air-core coils (spirals). The antennas canresonate even when both antennas are separated to the extent that thecoefficient of coupling k of the electromagnetic induction between theantennas is reduced to about 0.01. At the second type resonance of thepresent invention, the antenna circuits resonate by matching theimpedance Z and the induced resistance r, which is shown in Equations 24and 25 (Equations 30 and 31). The resonance is effective that theelectric power can be transferred from the power supply circuit 3 to theload circuit 4 in full efficiency. At the first type resonance of thepresent invention, matching the impedance Z and the induced resistancer, which is shown in Equations 33 and 34, is effective to transfer theelectric power in full efficiency from the power supply circuit 3 to theload circuit 4. The present invention can be applied also to thecircuits that fill the dielectric medium between the antennas instead ofthe vacuum and air, or to the circuits that fills the paramagneticmaterial between them. Moreover, the inductive power transfer circuitaccording to present invention is not limited to the usage alone inwhich the power is transferred for the energy supply. The inductiveelectric power transfer circuit according to present invention can beused to transfer the power from the transmitter antenna 1 to thereceiver antenna 2 for signal propagation.

First Embodiment

In the first embodiment of the inductive electric power transfer circuitis composed of receiver antenna buried inside of a body, and thetransmitter antenna out of the body, so that it transfers the electricpower between them through the skin of the body. The first embodiment isdescribed using FIG. 1 to FIG. 12.

In FIG. 1, transmitter antenna 1 is copper ribbon wiring whose width is1 mm and thickness is 50 μm, and has the shape of one turn coil on theplane whose diameter D is 46 mm. For instance, the transmitter antenna 1is formed on the polyimide film of 25 μm in thickness. The receiverantenna 2 can be made in a shape of coil, the coil diameter G is 50 mm,and the antenna wiring is covered with polyimide layer of 25 μm inthickness, so that it can be buried inside of a body by an operation.The terminal Port 1 (P1) of the power supply circuit 3 which feeds poweris connected in series with the transmitter antenna 1 at the middle ofthe antenna wiring. A feeder cable which connects the power supplycircuit 3 with the transmitter antenna 1 has the characteristicimpedance matched to the output impedance Z1 of the power supply circuit3. For instance, when the output impedance Z1 of the power supplycircuit 3 is 4Ω, the feeder cable has the matched characteristicimpedance of 4Ω. The feeder of the characteristic impedance can beobtained using a polyimide film that has the relative dielectricconstant of 3.5 and is 50 μm in thickness, and the copper wiring, 2.4 mmin width and 50 μm in thickness, on both side of the film. Both ends ofthe transmitter antenna 1 are connected to a capacitance C1 of 100 pF.The capacitance C1 of 100 pF can be formed with the wiring pattern thatconsists of two parallel square electrodes of 34 mm in length, and theyhave air gap of 0.1 mm between them. Additionally, the capacitance of100 pF can be formed with the pattern that consists of two parallelsquare electrodes of 46 mm×1.8 mm on both sides of a polyimide filmwhich is 0.025 mm in thickness and 3.5 in relative dielectric constant.The receiver antenna 2 is formed of a copper wiring of 1 mm in width and50 μm in thickness. The wiring is formed to one turn coil of 50 mm inthe coil diameter G, which is covered with polyimide films of 0.025 mmin thickness. The diameter of this receiver antenna 2 is different fromthe diameter of the transmitter antenna 1. Port 2 (P2) of the terminalof the load circuit 4 is connected in series at the midpoint of thewiring of the receiver antenna 2. Moreover, both ends of the receiverantenna 2 is connected to a capacitance C2 of 90 pF. As shown in theside view in FIG. 1( b), the transmitter antenna 1 and the receiverantenna 2 separate distance of spacing h between antennas axially of theantenna coil (in a direction perpendicular to the xy plane). Theinductive electric power transfer circuit in the circuit diagram in FIG.2( a) is composed. The power supply circuit 3 outputs the electriccurrent I1 to the transmitter antenna 1. The output current I1 is madeto return to the power supply circuit in positive phase. And the powersupply circuit is made to amplify the current so that the currentoscillates at the angular frequency ω of the resonance of the antenna.

(Induced Resistances of Antennas with which the Impedance of PowerSupply Circuit 3 and Load Circuit 4 are Matched)

Power transfer efficiency Pe was sought by the electromagnetic fieldsimulation about the third type resonance of the inductive electricpower transfer circuit. Power transfer efficiency Pe was sought by theelectromagnetic field simulation about the third type resonance of theinductive electric power transfer circuit, and the induced resistancesr1 and r2 generated are sought as follows. That is, the value of outputimpedance Z1 of power supply circuit 3, with which the power is mostefficiently transferred from the power supply circuit 3 to the loadcircuit 4, is sought. It is assumed that the value is the inducedresistance r1 of the transmitter antenna 1. And, it is assumed that thevalue of load impedance Z2 of load circuit 4, with which the power ismost efficiently transferred, is induced resistance r2 of receiverantenna 2. The graphs from FIG. 3 a to FIG. 3 c show the results of thesimulations about some spacing h between antennas. The graphs show Sparameters (S21) of power transmission from the power supply circuit 3to the load circuit 4 in decibels (dB) in the vertical axis. Thehorizontal axis of the graph is frequency f of the antenna current I1,which is the current on the transmitter antenna 1 passed from the powersupply circuit. FIG. 3( a) shows the result when spacing h betweenantennas of FIG. 1 is 1 mm. FIG. 3( b) shows the result when h=10 mm.FIG. 3( c) shows the result when h=20 mm. In FIG. 3( a), when spacing hbetween antennas is 1 mm, the induced resistance r1 of the transmitterantenna 1 is 20Ω, and the induced resistance r2 of the receiver antenna2 is 23Ω. When the impedance Z of the power supply circuit 3 and theload circuit 4 are matched to the corresponding induced resistances r,the antennas resonates and the power transmitting efficiency is thehighest. For example, the power transmitting efficiency is close to 100%when the frequency f of the antenna current I1 is 40 MHz. The spacing hbetween antennas is needed to be shorter than the near-field-distancewhich is calculated as (wavelength of resonant electromagneticfield)/(2π). In this embodiment, when the frequency f is 40 MHz, thewavelength of the electromagnetic field is about 7.5 m. So that, even ifspacing h between antennas is separated by 20 mm, the spacing h betweenantennas is sufficiently near as one-sixtieth of (wavelength of resonantelectromagnetic field)/(2π). In FIG. 3( b), when the spacing h betweenantennas is 10 mm, r1 is 8Ω and r2 is 9Ω. In FIG. 3( c), when thespacing h between antennas is 20 mm, r1 is 4Ω and r2 is 4Ω. Even ifspacing h between antennas is 20 mm in FIG. 3( c), S21 is −0.3 dB and 92percent of the electric power can be transferred.

As described above, close to 100% of the power is transferred when thespacing h between antennas is 1 mm, 10 mm, and 20 mm. There is afrequency band width (resonant frequency bandwidth) of the frequency fat which power is transferred efficiency close to 100%. When spacing hbetween antennas is 1 mm in FIG. 3( a), there is a frequency band from35 MHz to 55 MHz, so that the frequency band width is about 20 MHz. Theresonant frequency bandwidth where the power transfer efficiency closeto 100 percent narrows as the spacing h between antennas grows. In FIG.3( b), when the spacing h between antennas is 10 mm, the resonantfrequency band is from 36 MHz to 46 MHz and the resonant frequency bandwidth is about 8 MHz. In FIG. 3( c), when the spacing h between antennasis 20 mm, the resonant frequency band is from 38 MHz to 41 MHz and theresonant frequency band width is about 3 MHz.

In FIGS. 3( a) to 3(c), the resonant frequency f given by the simulationis 40 MHz. Since the capacitance C1, to which both ends of thetransmitter antenna 1 is connected, is 100 pF, theeffective-self-inductance L1 of the transmitter antenna 1 is calculatedand the result is 160 nH. Since the capacitance C2, to which both endsof the receiver antenna 2 is connected, is 90 pF, theeffective-self-inductance L2 of the receiver antenna 2 is 180 nH. Whenthe capacitances C, that connects both ends of these antennas, aregreater than these values, the distribution of the electric current onthe antenna seems to have the same value to the edge of the antennawiring, and the current is equal anywhere on the antenna. Therefore,when those capacitances C are greater than these values, the effectiveself-inductances L of the antenna seem to have constant values.

In the graph in FIG. 4, the black circle denotes the value that iscalculated as the induced resistance r1 which is obtained by simulationis divided by (2πfL1) in the vertical axis. The value of r1/(2πfL1) isnon-dimensional parameter. A white circle denotes the value that iscalculated as r2 is divided by (2πfL2), and the value of r2/(2πfL2) isnon-dimensional parameter. The graph of FIG. 4 shows these values as afunction of the non-dimensional parameter (h/√(D×G)), which is thespacing h between antennas divide by the square root of the product ofthe coil diameters D and G. In the graph of FIG. 4, the solid linedenotes the calculated value by the following approximate Equation 36.

(Equation 36)

r/(2πfL)=1.8 EXP(−4.3√/(0.04+√(1/t ²−1)))

(Equation 37)

t=√(D×G/(((D+G)/2)² +h ²))

Where, the value t in the approximate Equation 36 is given by Equation37. In FIG. 4, approximate Equation 36, which is shown as the solidline, agrees with the simulation result well.

Since the value of the longitudinal axis of FIG. 4 is same as Equation30 and Equation 31, the longitudinal axis shows the coefficient ofcoupling k of the electromagnetic induction of the transmitter antenna 1and the receiver antenna 2. In order to verify it, following Equation 38was made by calculating the coefficient of coupling k of theelectromagnetic induction between both coils theoretically and strictly,when the transmitter antenna 1 is a circular coil of the circular coilof D in the diameter of G in the diameter in receiver antenna 2.

Where the coefficient A in the Equation 38 is given by Equation 39

(Equation 38)

k=A×((−t+2/t)×K(t)−(2/t)×E(t))

(Equation 39)

A=μ√(D×G/(L1×L2))/2

Where, μ is permeability, t is defined by Equation 37, K(t) is completeelliptic integral of the first kind, E(t) is complete elliptic integralof the second kind.

The following approximate Equation 40 is obtained from this Equation.

(Equation 40)

k=4.86 A{1.8 EXP(−4.3√(0.04+√/(1/t ²−1)))}

Substituting L1=160 nH, L2=180 nH, and space permeability μ=1.26 μΩ·s/minto the formula of A, 4.86 A, which is the first coefficient ofEquation 40, becomes 0.88. That is about one in the error margin ofabout 10 percent. That is, the coefficient of coupling k of theelectromagnetic induction between both coils, which is given withEquation 40, approximates the k value obtained with Equation 36, in theerror margin of about 10 percent. Therefore, the vertical axis of thegraph of FIG. 4 agrees with coefficient of coupling k of theelectromagnetic induction of the transmitter antenna 1 and receiverantenna 2. In the graph of FIG. 4 the solid line denotes the value givenwith the approximate Equation 36, which is approximated to thecoefficient of coupling k of electromagnetic induction between bothantennas. In FIG. 4, the coefficient of coupling k calculated byapproximate Equation 36 well agreed with the value r/(2πfL) given by thesimulation. Therefore, it can be said that the simulation result agreeswith the calculated result of Equation 30 and Equation 31.

(Bandwidth of Frequency in Which Power Transfer Efficiency is Saturated)

In FIG. 4, when h=1 mm and (h/√(D×G)) is 0.02, coefficient of coupling kis 0.5 and induced resistance r is about 20Ω. When h=10 mm and(h/√(D×G)) is 0.2, coefficient of coupling k is 0.2 and inducedresistance r is about 8Ω. When h=20 mm and (h/√(D×G)) is 0.4,coefficient of coupling k is 0.1 and induced resistance r is about 4Ω.The graph in FIG. 3( a) shows the transmitting efficiency Pe of theelectric power as a function of frequency by S parameter S21 when h=1mm, coefficient of coupling k=0.5, and induced resistance r is about20Ω. The graph in FIG. 3( b) shows the S-parameter when the inducedresistance r is 8Ω and the coefficient of coupling k is 0.2 in h is 10mm. The graph in FIG. 3( c) shows the S-parameter when the inducedresistance r is 4Ω and the coefficient of coupling k is 0.1 in h is 20mm. In these graphs of FIG. 3, the upper limit of the bandwidth offrequency f with which transmitting efficiency Pe of the power issaturated is almost f/fo=1/√(1−k), and the lower bound is almostf/fo=1/√ (1+k). Therefore, when coefficient of coupling k is enlarged,it is effective that ratio f/fo of the bandwidth of frequency f withwhich transmitting efficiency Pe of the power is saturated can beenlarged into the width of coefficient of coupling k. Therefore, whencoefficient of coupling k is enlarged, the frequency band in which powertransfer efficiency Pe from transmitter antenna 1 to receiver antenna 2is saturated can be enlarged. It is effective in fully matching theresonant frequency of both antennas by loose accuracy, and it becomeseasy to manufacture and to adjust both antenna circuits.

Since in this embodiment, the bandwidth of frequency f with whichtransmitting efficiency Pe of the power is saturated is width ofcoefficient of coupling k in ratio f/fo, the bandwidth of frequency f ofthe inductive electric power transfer circuit, which transfer the power,can secure the width of 0.4% or more of the resonant frequency bysetting coefficient of coupling k of transmitter antenna 1 and receiverantenna 2 to 0.004 or more. Therefore, it is desirable to adjustcoefficient of coupling k to 0.004 or more. In that case, the effectthat the gap of the resonant frequency of both antennas is installingwithin the range without the obstacle to transfer the power is achievedbecause it can be comparatively facilitated to make the difference ofthe resonant frequency of transmitter antenna 1 and receiver antenna 2within 0.4% by making differences of characteristics of parts used forthe inductive electric power transfer circuit within 0.4%.

Thus, it is effective in this embodiment that the power can beefficiently transferred by transferring the power from transmitterantenna 1 in vitro to receiver antenna 2 in vivo by high frequency f of40 MHz, and matching impedance Z1 and Z2 of power supply circuit 3 andload circuit 4 with induced resistance r1 and r2, which is from 20Ω to4Ω. This effect is achieved by making the distance between antennasbelow (wavelength of the electromagnetic field with which the antennaresonates)/(290 ), which is in near field. The inductive electric powertransfer circuit of this embodiment has little output impedance Z1 ofpower supply circuit 3, which is matched to the induced resistance r totransfer the power, and input impedance Z2 of load circuit 4, which ismatched to the induced resistance r to transfer a prescribed power, suchas 20Ω to 4Ω. Therefore, the voltage of circuit can be lower, beingeffective in high safety in the power transfer circuit. In thisembodiment, it is effective that the power can be transferred bynon-contact in the efficiency of 92% from the circuit in vitro to thecircuit in vivo separated by the tissue 20 mm in thickness. Moreover,the receiver antenna 2 is effective in burring in vivo easily becausethe antenna can be small and thin, such as 50 mm square antenna and theantenna has the wiring of the copper 50 μm in thickness and 1 mm inwidth covered with the insulator 25 μm in thickness.

(Modification 1)

Modification 1 composes the inductive electric power transfer circuit,in which the angular frequency ω of the current is lower than that forthe first embodiment, which supplies power to the receiver antenna 2 invivo buried. In modification 1, capacitance C1 between the ends of thetransmitter antenna 1 and capacitance C2 between the ends of thereceiver antenna 2 are almost four times of them in the firstembodiment, such as C1=400 pF and C2=360 pF. FIG. 5 shows the graph forS-parameters (S21 s) of the power transmission given by simulation as afunction of frequency f. In the graph of FIG. 5, resonant frequency f,at which the power is transferred, is 20 MHz, which is half of that inthe first embodiment. FIG. 6 shows the graph for the induced resistancer in modification 1, which is represented by r/(2πfL) that iscoefficient of coupling k and a non-dimensional parameter, as a functionof spacing h between antennas, which is represented by (h/√(D×G)) thatis a non-dimensional parameter. In FIG. 6, similarly to FIG. 4, theblack circle and the white circle denote the result in simulation, andthe solid lines denote the calculated value using approximate Equation36. Also in FIG. 6, the simulation result well agreed with thecalculated results using approximate Equation 36. In FIG. 6, when h=1 mmand (h/√(D×G)) is 0.02, coefficient of coupling k is 0.5 and inducedresistance r is about 10Ω. When h=10 mm and (h/√(D×G)) is 0.2,coefficient of coupling k is 0.2 and induced resistance r is 4Ω. Whenh=20 mm and (h/√(D×G)) is 0.4, coefficient of coupling k is 0.1 andinduced resistance r is 2Ω. When resonant frequency, f, becomes halffrom FIG. 4 to FIG. 6, induced resistances, r, become half.

(Modification 2)

Modification 2 composes the inductive electric power transfer circuitwhich transfers electric power through the wall of a house. Transmitterantenna 1 and receiver antenna 2 are made the antenna of the same size,which has diameter, D, of 50 mm both in length and in breadth, and areformed on the polyimide membrane of 50 μm in thickness, respectively.The antenna-wiring is 1 mm in width and is made of copper of 50 μm inthickness, and the capacitance C1 and C2, which is between both ends ofeach antenna, are adjusted to 100 pF. The antenna-wiring is covered withprinted solder resist of almost 30 μm in thickness or insulating filmsuch as polyimide membrane etc. In this case, shifting distance d, whichis the length to move the receiver antenna 2 from transmitter antenna 1in the direction X and Y of a horizontal plane (XY plane), was set tozero and the case was simulated. As a result, it is confirmed that theantenna current resonates at frequency f of 37.4 MHz, and it hasunderstood that the effective self-inductance of the antenna isL1=L2=L=176 nH. FIG. 8 shows the graph for the induced resistance r,which is represented by the non-dimensional parameter ofr/(2πfL)=coefficient of coupling k, as a function of the spacing hbetween antennas, which is represented by the non-dimensional parameter(h/D). The graph of FIG. 8 shows the resistances at the cases wherespacing h between antennas, which is between antennas in the directionof the antenna-coil-axis, is from 2 mm to 50 mm. In the graph of FIG. 8,the black circle denotes r obtained from the simulation, and the solidline denotes that calculated using approximate Equation 36. The valuesobtained from simulation well agree with those calculated using theapproximate Equation 36.

In FIG. 8, when (h/D) is 1, induced resistance r is 0.8Ω and coefficientof coupling k is almost 0.02. When (h/D) is two, induced resistance r ofthe simulation result is 0.24Ω and coefficient of coupling k is 0.006,and, power transfer efficiency, Pe, is 22 percents. Since the rate offrequency, f/fo, with which power-transmitting-efficiency, Pe, issaturated has a band-width which is almost same as the coefficient ofcoupling k, when coefficient of coupling k is 0.006, the bandwidth offrequency f with which power transfer efficiency Pe is saturated isalmost 0.6% of resonant frequency fo. Therefore, even though parts whichare almost 0.6 percents different in characteristics from the designedones are used, it is effective that the difference of the resonantfrequency of the transmitter antenna 1 and the receiver antenna 2 can bestopped in the tolerance. Thus, it is effective for composing apractical inductive electric power transfer circuit to make the spacing,h, between the coiled transmitter antenna 1 and receiver antenna 2within twice the diameter D of the coils of the antennas.

The graph of FIG. 9 shows the power transfer efficiency Pe in themodification 2 as a function of (h/D) at 37 MHz of resonant frequency fwith the antenna whose wiring is copper of 1 mm in the width.

In FIG. 9, the power transfer efficiency Pe decreases as (h/D) grows.The reason is that as (h/D) grows coefficient of coupling k becomessmall and induced resistance r1 and r2 calculated with Equations 24 and25 become small, as a result, the power transfer efficiency Pecalculated with Equation 29 becomes small. In FIG. 9, even thoughspacing h between antennas is separated as large as 50 mm that is thesame distance as coil diameter D(h/D=1), the power transfer efficiencyis almost 75%, so that the power can be transferred efficiently. Forexample, the transmitter antenna 1 and the receiver antenna 2 with coilof 50 mm in diameter D are set separated by a wall of 50 mm inthickness, and the power supply circuit 3 is in the house. The devicesupplies the power to the outdoor load circuits 4 such as illuminatingdevice or display device outside the house, by opposing them innon-contact in the efficiency of almost 75% without making a hole forwiring through the wall of the house.

When induced resistance r is enlarged by increasing the number ofrolling of coils (spiral) of the wiring for the antenna, the effectiveinductance L more increases than the conductive resistance of theantenna-wiring. That is effective to enlarge the power transferefficiency Pe according to the Equation 29 for power transfer efficiencyPe. On the other hand, when the capacitor C1 and C2 (capacitanceelement), which connect to both ends of each antenna, become largecapacitance, the resonance angular frequency ω becomes small to decreaseinduced resistance r, so that the power transfer efficiency Pe becomessmall according to Equation 29.

(Modification 3)

Modification 3 composes the inductive electric power transfer circuit inwhich the power is transferred through the wall of the house, and on thecircuit the angular frequency ω of the current is reduced. The casewhere the capacitance C1 between the edges of transmitter antenna 1, andC2 of receiver antenna 2 are set up 400 pF, which is four times of thatin the modification 2, is simulated, and resonant frequency f can bereduced to almost 20 MHz, which is half in modification 2. FIG. 10 showsthe graph for induced resistance r, which is represented by thenon-dimensional parameter r/(2πfL), as a function of spacing h betweenantennas, which is represented by the non-dimensional parameter (h/D).In FIG. 10, the black circles denote induced resistances r=r1=r2according to simulation, and the solid line denotes them calculatedusing approximate Equation 36. Also in FIG. 10, the simulation resultwell agreed with that calculated using approximate Equation 36.

(Modification 4)

Modification 4 composes the inductive electric power transfer circuitthat transfers the power through an insulating material such as a wallof a house. The circuit uses the antennas facing each other in parallelas shown in FIG. 7 in which the receiver antenna 2 is shifted from thetransmitter antenna 1 on XY-antenna-plane by the length d in thedirection of both X-axis and Y-axis. In this inductive electric powertransfer circuit, when the capacitance C1, between the edges of thetransmitter antenna 1, and C2, between the edges of the receiver antenna2, is fixed to 100 pF and spacing h between antennas is fixed to 2 mm,the matching condition of the circuit were obtained as a function of theshifting distances d with simulation. The result is described asfollows. Resonant frequency f of the antenna circuit in this case wasfixed to fo of 37.4 MHz which is same as the modification 2. FIG. 11shows the graph for induced resistance r, which is represented by thenon-dimensional parameter r/(2πfL), at the resonant frequency f=37.4 MHzas a function of shifting distance d of the coil, which is representedby the non-dimensional parameter (d/D), where the black circles denotethe results obtained from the simulation. Induced resistance r thatappears on the antenna decreases when the position of the coil shiftedhorizontally. The cause of this effect is that coefficient of coupling kof the electromagnetic induction of the coil becomes small when theposition of the coil is shifted.

FIG. 12 shows the graph for the power transfer efficiency from the powersupply circuit 3 to the load circuit 4 as a function of shiftingdistance d of the coil, which is represented by the non-dimensionalparameter (d/D). FIG. 12 shows that, when (d/D) is not more than 0.4,that is the shifting distance d is not more than 20 mm, then the powertransfer efficiency is not less than 90%, the power can be transferredvery efficiently. The power transfer efficiency becomes zero at theposition in which (d/D)=0.66, where d is shifting distance of the coil.The cause of this effect is as follows. The sum of the magnetic fieldthat is enclosed within the coil becomes zero at this layout because thedirection of the magnetic field passes the coil area reverses by theplace in the coil of the antenna. Therefore, induced voltage andcoefficient of coupling k becomes zero at this layout. In FIG. 12, thepower transfer efficiency will recovers when (d/D) exceeds 0.4.

When the axis of the coil of this transmitter antenna 1 and receiverantenna 2 is only horizontally shifted by 100 mm, which is twice thedistance of coil diameter D=50 mm of the antenna, induced resistance rbecomes 0.23Ω, and r/(2πfL), which is equal to coefficient of coupling kof the coil of the antenna system, becomes 0.005, so that the powertransfer efficiency Pe becomes 20%. Thus, when the axis of the coil ofthe antenna is shifted twice or less of the antenna-coil-diameter D,coefficient of coupling k of the antenna becomes 0.005 or less andbandwidth of frequency f, with which power transfer efficiency Pe issaturated, becomes 0.5% of resonant frequency fo. Therefore, even thoughcomponents with tolerance of 5%s are used, the difference of theresonant frequency of transmitter antenna 1 and receiver antenna 2 canbe restricted within tolerance. Therefore, a practicable inductiveelectric power transfer circuit, whose antennas are coils with diameterD, can be made by shifting the receiver antenna 2 from the transmitterantenna 1 by shifting distance d which is within twice theantenna-coil-diameter D.

The coefficient of coupling k between transmitter antenna 1 and receiverantenna 2 is not restricted over 0.004. When the coefficient of couplingk is smaller than that, the inductive electric power transfer circuit towhich the power is efficiently transferred can be composed by adding thecircuit that tunes resonant frequency f of the transmitter antenna 1 tothe resonant frequency of the receiver antenna 2.

Second Embodiment

The second embodiment composes the inductive electric power transfercircuit that supplies the power from the transmitter antenna 1 in vitroto the receiver antenna 2 in vivo through the outer skin. The inductiveelectric power transfer circuit is adapted to the circumstances that theposition of the transmitter antenna 1 and receiver antenna 2 are notsteady and coefficient of coupling k of electromagnetic inductionchanges, to keep the stability of power transfer. In this embodiment,the inductive electric power transfer circuit is composed of thetransmitter antenna 1 and the receiver antenna 2 in FIG. 7, and theantennas are operated at the second type resonance of the principle ofthe present invention.

FIG. 13( a) shows the power transfer efficiency (%) as a function ofimpedance Z, which is represented by the non-dimensional parameterZ/(2πfL), of power supply circuit 3 and load circuit 4 when theantenna-spacing h between transmitter antenna 1 and receiver antenna 2in FIG. 7( a) is 10 mm (h/D=0.2).

In FIG. 13( a), the solid line shows the power-transfer-efficiency whenfrequency f of electric current I1, which is supplied from the powersupply circuit 3 to transmitter antenna 1, is fixed to 37.4 MHz. Thedotted line shows the power-transfer-efficiency for the secondembodiment, in which the frequency f of the electric current I1 isadapted and adjusted to the frequency in which the maximum power istransferred.

FIG. 13( b) shows the graph for power transfer efficiency Pe, which isrepresented by S-parameters (S21) in dB, as a function of frequency f ofthe antenna current when the impedance Z is fixed in the inductiveelectric power transfer circuit. The horizontal axis in FIG. 13( b)denotes frequency f of the antenna current. In FIG. 13( a), whenZ/(2πfL) is larger than 0.22 (Z is 9Ω in this case), the transmissionefficiency of the power decreases. This value 0.22 is equal tocoefficient of coupling k of the electromagnetic induction. On the otherhand, when Z/(2πfL) is smaller than 0.22 (Z is 9Ω in this case), whichis the value of the coefficients of coupling k, the graph splits intotwo graphs according to conditions described below. (1) When frequency fof the transferring power is fixed to 37.4 MHz, the transmissionefficiency of the power decreases as impedance Z of power supply circuit3 and load circuit 4 decreases more than induced resistance r. (2) Onthe other hand, the power transfer efficiency hardly decreases as shownby the broken line in FIG. 13( a) when frequency f of the antennacurrent is adjusted in order to transfer maximum power which is at oneof the two peaks of S21 (which represents power transfer efficiency, Pe)in FIG. 13( b). In the second embodiment, the resonance frequency f isadjusted to the frequency in which the power is transferred at maximumpower transfer efficiency, Pe.

The inductive electric power transfer circuit of the second embodimentcomposes the inductive electric power transfer circuit that adjusts tokeep the second type resonance, in which ω is not ωo, of the principleaccording to present invention even when the position of transmitterantenna 1 and receiver antenna 2 and coefficient of coupling k of theelectromagnetic induction are not steady. In the second embodiment,input impedance Z2 of the load circuit 4 is fixed to Z1×(L2/L1), andoutput impedance Z1 of the power supply circuit 3 is fixed to a valuesmaller than the upper limit of induced resistance r1. The resonanceangular frequency ω of the electric current of power supply circuit 3 isadjusted to keep the resonance when the value of coefficient of couplingk changes due to the change of the distance between the transmitterantenna 1 and receiver antenna 2. For this purpose, the resonantfrequency adjustment circuit that changes the angular frequency ω intothe value that most enlarges electric current I1 of transmitter antenna1 is built into the power supply circuit 3 and changes the angularfrequency ω into the value that cause the largest resonant electriccurrent by returning the current of the transmitter antenna 1 to thepower supply circuit 3 with the positive-feedback circuit from the powersupply circuit 3. The adjusted value of the angular frequency ω issquare root of the reciprocal of L1·C1·(1+k·cos (β)). So that, theinductive electric power transfer circuit of the second embodimenttransfers the power at maximum efficiency by self-adjusting the angularfrequency ω of the current from the power supply circuit 3.

In the second embodiment, the phase angle β changes from (π/2) when ω ofEquation 28 changes from ωo of Equation 19. Therefore, cos (β) changesfrom zero to limits, ±1. And the resonance-angular-frequency ω ofEquation 28 changes from ωo to the ω of Equation 41.

(Equation 41)

ω≈ωo/√(1±k)

Then, sin (β) changes from one to about zero, and induced resistance r1and r2 in Equations 24 and 25 are reduced less than kωL1 and kωL2 of theupper limit values.

Thus, in the second embodiment, the resonance-angular-frequency ω shiftsfrom ωo so that the small induced resistances r1 and r2, which arecalculated with Equations 24 and 25, match to the output impedance Z1 ofpower supply circuit 3 and to the load impedance Z2 of load circuit 4,so as to transfer the power in complete efficiency. In this case,because the ratio of induced resistance r1 and r2 becomes the ratio ofeffective-self-inductance L1 and L2, the ratio of the output impedanceZ1 of the power supply circuit and the input impedance Z2 of the loadcircuit is fixed to the ratio of effective-self-inductances L1 and L2.Thus, the inductive electric power transfer circuit of the secondembodiment is effective to keep the power transmission in fullefficiency and to keep the resonance of the antenna circuit even if thedistance between antennas is not stable.

Third Embodiment

In the third embodiment, the inductive electric power transfer circuittransfers electric power through a wall of a house. The inductiveelectric power transfer circuit has many turned spiral wiring forantennas, so that induced resistance of the antenna is great and isclose to the characteristic impedance of the feeder, which connects thepower supply circuit 3 to the transmitter antenna 1 and transfers power.This inductive electric power transfer circuit is operated at the thirdtype resonance of the principle of the present invention. FIG. 14( a)shows a front view of the transmitter antenna 1 and the receiver antenna2 which are in the inductive-electric-power-transfer-circuit for thethird embodiment. FIG. 14( b) shows a side view of them. Similarly tothe first embodiment, the power supply circuit 3 is connected to thetransmitter antenna 1 and the load circuit 4 is connected to thereceiver antenna 2. In FIG. 14, the transmitter antenna 1 is composed asfollows. The antenna is a 3-turn copper coil whose diameter D is 54 mmset on a polyimide film whose thickness is 50 μm. The coil is a linewhich is 1 mm in width and is 50 μm in thickness. Both ends of theantenna are connected to C1 of 280 pF in capacitance. Port 1 (P1) isconnected to the middle of the antenna to feed power from the powersupply circuit 3. The receiver antenna 2 is the same in size and shapeas the transmitter antenna 1, which is three turned coil and whosediameter is 54 mm in square. Both ends of the antenna is connected tothe capacitance C2 of 280 pF. And port 2 (P2), which is the terminal ofload circuit 4, is set at the middle of the antenna. FIG. 14( b) shows aside view of the coils of the transmitter antenna 1 and the receiverantenna 2, which are placed in parallel with each other. They areseparated by spacing h between antennas in the vertical direction tocoil level (XY-plane), and their axis of the coil are shifted byshifting distance d of 7 mm in the direction of X-axis without shiftingin the direction of Y-axis.

The result of simulation is that resonant frequency f is 9 MHz andeffective-self-inductance L1 of the transmitter antenna 1 andeffective-self-inductance L2 of the receiver antenna 2 are 1.2 μH,respectively. In this embodiment, since both transmitter antenna 1 andreceiver antennas 2 are three turned coils, whose number of turn isthree times the number of turns of coils in the first embodiment,effective-self-inductances L=L1=L2 of the antennas are almost seven,which is almost square of the number of turns of the coils, times the Lof the antennas in the first embodiment. A graph for transmittingefficiency of power as a function of frequency, the graph whose shape issimilar to FIG. 3 and which shows resonant frequency f=9 MHz, isobtained. In this embodiment, since effective-self-inductance L is seventimes the L of the first embodiment, though the frequency f of theresonance reduces from 40 MHz of the first embodiment to 9 MHz, therebyincreasing value kωL of induced resistance r more than the firstembodiment. Then, the impedances Z of power supply circuit 3 and theload circuit 4 are matched and become large. There is an effect thatwhen induced resistance r grows, power transfer efficiency Pe grows,which is calculated with Equation 29.

FIG. 15( a) shows a graph for the induced resistance r, which isrepresented by non-dimensional parameter r/(2πfL), as a function ofspacing h between antennas, which is represented by non-dimensionalparameter (h/D), when resonant frequency f is 9 MHz in the thirdembodiment. In FIG. 15( a), the black circles denote data obtained bysimulation, and the solid lines denote data calculated using approximateEquation 36. The data obtained by simulation roughly agreed with datacalculated using approximate Equation 36 in FIG. 15( a). FIG. 15( b)shows the graph for power transfer efficiency from power supply circuit3 to load circuit 4 as a function of spacing h between antennas, whichis represented by non-dimensional parameter (h/D). FIG. 15( b) showsthat power can be transferred in the power transfer efficiency of almost90%, which is very efficient, when spacing h between antennas is almost60 percent of coil diameter D (h/D=0.6), where spacing h betweenantennas is almost 30 mm.

(Modification 5)

In modification 5; the capacitance C1 between the edges of thetransmitter antenna 1 and the capacitance C2 between the edges of thereceiver antenna 2 are 1/16 capacitances of the third embodiment, thecapacitances are 17 pF. In modification 5, the resonant frequency frises to 35 MHz. FIG. 16A shows the graph for the induced resistance r,which is represented by non-dimensional parameter r/(2πfL), as afunction of spacing h between antennas, which is represented bynon-dimensional parameter (h/D). Since the capacitances C1 and C2, whichare between ends of antenna, are reduced to one-sixteenth capacitancesof third embodiment; the resonant frequency f becomes four times thefrequency of third embodiment, the resonant frequency becomes 35 MHz. Asshown in FIG. 16( a), the result of simulation, which is denoted byblack circle, roughly agreed with the result calculated usingapproximate Equation 36, the result of Equation 36 is denoted by solidline. FIG. 16B shows the graph for power transfer efficiency from thepower supply circuit 3 to the load circuit 4 as a function of spacing hbetween antennas, which is represented by non-dimensional parameter(h/D). FIG. 16B shows that; power transfer efficiency is almost 90% whenspacing h between antennas is 40 mm, which is 80 percent of coildiameter D, (h/D=0.8), then the power is transferred very efficiently.FIG. 16B shows that; when spacing h between antennas rises 1 mm and(h/D) is 0.6, coefficient of coupling, k=r/(2πfL), becomes almost 0.6,and induced resistance r becomes 158Ω. In this embodiment, sinceeffective inductance L rises to seven times inductance of firstembodiment; at 35 MHz in this embodiment, value of induced resistance,r=kωL, rises seven times resistance of first embodiment at 40 MHz; andimpedances Z in power supply circuit 3 and load circuit 4 that arematched to the induced resistances rise seven times impedances of firstembodiment. An effect that power transfer efficiency Pe rises when theinduced resistance r grows, is shown by Equation 29.

Fourth Embodiment

The fourth embodiment composes the inductive electric power transfercircuit which has a feeder with high characteristic impedance from powersupply circuit 3 to transmitter antenna 1, and the circuit has raisedinduced resistance of antenna by raising resonant frequency f of thethird embodiment by removing external capacitor between both ends ofantenna. That is, in the fourth embodiment, both ends of the transmitterantenna 1 of FIG. 14 are opened, and both ends of the receiver antenna 2are opened. There is no external capacitor between the ends of theantennas, but there are parasitic capacitance, whose value is defined asmin, between the ends as capacitance C1 and C2. This inductive electricpower transfer circuit is operated in the third type resonance of theprinciple of the present invention. The antenna system for the inductiveelectric power transfer circuit of the fourth embodiment resonates byfrequency f=154 MHz. Calculating the parasitic capacitance (min) betweenends of a coiled antenna, the parasitic capacitance yields 1 pF usingresonant frequency f=154 MHz and effective self-inductance L=1.2 μH ofantenna coil in which an external capacitor is added. That is, eventhough without external capacitor between both ends of antenna wiring,the antenna can be represented by a circuit in FIG. 2A. In the circuit,capacitance C1 of almost 1 pF is connected between both ends oftransmitter antenna 1, and capacitance C2 of almost 1 pF is connectedbetween both ends of receiver antenna 2.

FIG. 17A shows a graph for induced resistance r, which is represented bynon-dimensional parameter r/(2πfL), of the fourth embodiment at resonantfrequency f=154 MHz as a function of spacing h between antennas, whichis represented by non-dimensional parameter (h/D). In calculating r/(2πfL), the effective self-inductance L is 1.2 μH, which is obtained whenan external capacitor is added to the coil of the antenna. The blackcircle denotes simulation result and the dotted line denotes (2/π) timesthe value that is calculated with approximate Equation 36. When anexternal capacitor but parasitic capacitance is not added between endsof an antenna, the antenna current becomes small as it approaches theends of the antenna, which is different from when an external capacitoris added between the ends of the antenna. The average value of theantenna current is (2/π) times the value of electric current at the portin the middle of the antenna. Therefore, a dotted line shows a graph for(2/π) times, in which the value of right side of approximate Equation 36is multiplied by (2/π) to substitute the value of average antennacurrent for the value of port current. The substituted value agreed withvalue obtained from the simulation. The reason why this substitution ofthe value is needed is that the effective self-inductance L of theantenna coil changes according that both ends of the antenna areconnected with an external capacitor or are without that. L used inapproximate Equation 36 is executed self-inductance L that changesaccording to distribution of the antenna current. The value of effectiveinductance L of antenna when both ends of the antenna are free is (2/π)times the value of L when both ends of the antenna are connected withbig capacitance, so that approximate Equation 36 is used with replacingthe value of effective inductance L that was obtained when an externalcapacitor is connected with both ends of the antenna.

FIG. 17A shows that when spacing h between antennas is 4 mm, (h/D) is0.074, R/(2πfL) becomes 0.22 and induced resistance r becomes 260Ω.According to the fourth embodiment, induced resistance r is adjusted toalmost 260Ω by setting the spacing h between antennas to almost 4 mm.The value of induced resistance r matches well with characteristicimpedance of feeder in two parallel lines. The characteristic impedanceof feeder in two parallel lines is 277Ω when distance between the twoparallel lines is ten times the radius of the lines, so that thecharacteristic impedance is close to 260Ω which is the value of theinduced resistance r. According to the fourth embodiment, the inducedresistance r and the characteristic impedance of feeder, which matchesthe induced resistance, are high, so that electric current on thefeeder, which transfers power, is low, thereby reducing the loss causedby the electric current on resistive conductor of feeder.

FIG. 17B shows a graph for power transfer efficiency from power supplycircuit 3 to load circuit 4 as a function of spacing h between antennas,which is represented by non-dimensional parameter (h/D). FIG. 17B showsthat there is almost 90% power transfer efficiency when spacing hbetween antennas is almost 43 mm, which is 80% of coil diameterD(h/D=0.8), thereby power can transfer very efficiently.

Fifth Embodiment

The inductive electric power transfer circuit according to a fifthembodiment has a transformer using the second type resonance of theprinciple of the present invention. That is, the inductive electricpower transfer circuit is shown in FIG. 2A, where a transmitter antenna1 and receiver antenna 2 are air-core coiled, and the distance betweenthe antennas is less than one for 2π the wavelength of resonantelectromagnetic wave. The circuit has the transformer that convertsoutput impedance Z1 of power supply circuit 3 into load impedance Z2 ofload circuit 4. The load impedance Z2 is (L2/L1) times Z1. The ratiobetween the impedances is adjusted by changing the self-inductance L1and L2 by changing number of turns of the air-core coiled antennas.

The circuit according to the fifth embodiment uses the second typeresonance of the principle of the present invention in which theresonance angular frequency ω is different from ωo and inducedresistance r of the coiled antenna changes according to Equations 24 and25, in which induced resistance r is proportional to effectiveself-inductance L of the coiled wiring antenna and the proportionalfactor is product of coefficient of coupling k, 2πf, and sin (β). Thereis an effect that the transformer can convert output impedance of thepower supply circuit 3 connected with the transmitter antenna, impedancewhich is not more than kωL1, into the impedance seen from the receiverantenna, impedance which is not more than kωL2. According to the fifthembodiment, the transmitter antenna 1 and the receiver antenna 2 arecopper-spiral patterns, which are air-coiled wiring patterns, they areformed by etching copper foils on polyimide films. The space between theantennas is filled with air or insulating material withoutferromagnetism. When the antennas are set close to each other,coefficient of coupling k becomes high, so that upper limit of impedancethat can be converted with the transformer can be high. Therefore, it isdesirable to set the antennas close to each other in the air (orinsulating resin). In this transformer, impedance conversion rate(L2/L1) is designed by setting effective self-inductances L1 oftransmitter antenna 1 and L2 of receiver antenna 2 by setting number ofturns of coils of the antennas. Effective self-inductance L of thecoiled wiring of the antenna almost changes in proportion to the squarenumber of turns. Thus, the transformer according to fifth embodiment isan inductive electric power transfer circuit that converts impedance Z1of power supply circuit 3 to impedance Z2 of load circuit 4, andtransfers almost 100% power from power supply circuit 3 to load circuit4.

The transformer according to the fifth embodiment is designed thatoutput impedance Z1 of power supply circuit 3 is matched to inducedresistance r1 of transmitter antenna 1, and input impedance Z2 of loadcircuit 4 is matched to induced resistance r2 of receiver antenna 2.Induced resistances r1 and r2 which is matched to impedances Z1 and Z2are reduced by reducing sin (β) of Equations 24 and 25.

The resonant angular frequency ω that satisfies the impedance matchingcondition varies from ωo to (ωo/√(1±k)), which is shown in Equation 41,according to β as shown in Equation 28. According to Equation 28, whencos (β) is negative, the resonant angular frequency ω shifts higher thanωo to the right peak in the graph of FIG. 12B. Then, the current I2 onreceiver antenna 2 flows in the opposite direction of the current I1 ontransmitter antenna 1, canceling effect of each other, so that wholeantenna system generates little electromagnetic field into space,thereby reducing electromagnetic emission noise (EMI) caused by thetransformer.

When cos (β) is positive, the resonance angular frequency ω shifts lowerthan ωo to the left peak in the graph of FIG. 12B. Then, the current I2on receiver antenna 2 flows in the same direction of the current I1 ontransmitter antenna 1, so that there is a problem that whole antennasystem generates great electromagnetic field into space. However, thereis a utility that plural receiver antennas 2 can be set in parallel asthe antennas are in common with the axis of the coiled wiring of theantennas. Therefore, the plural receiver antennas 2 can receive inducedelectric power simultaneously.

The transformer according to the fifth embodiment can be reduced inweight and size when air-coiled antennas, which are a transmittingantenna 1 and a receiver antenna 2, and are separated by a distance lessthan 1/(2π) of the wavelength of resonant electromagnetic wave; arefaced each other in the air or insulating resin. Moreover, there isusefulness that the transformer according to fifth embodiment can beused at high frequencies without restriction, frequency in whichconventional transformer with a ferromagnetic core cannot be used due tofrequency characteristics of the ferromagnetic substance.

Sixth Embodiment

An inductive electric power transfer circuit according to a sixthembodiment is in an integrated circuit, and transfers electric powerbetween trace layers. FIG. 18A shows a plan view of a transmitterantenna 1 and a receiver antenna 2 according to sixth embodiment, andFIG. 18B shows a side view of them. This inductive electric powertransfer circuit is operated at the third type resonance of theprinciple of the present invention. A terminal Port 1 (P1) to a powersupply circuit 3 is set up in the middle of the wiring of thetransmitter antenna 1, and a terminal Port 2 (P2) to a load circuit 4 isset up in the middle of the wiring of the receiver antenna 2. FIG. 18Aand FIG. 18B shows coils of the transmitter antenna 1 and the receiverantenna 2 whose sizes are 1/1000 of the coils according to the thirdembodiment. The coils are made of copper in each trace layer in a chipof the integrated circuit, and are 1 μm in thickness. That is, thetransmitter antenna 1 and the receiver antenna 2 are three-turned coilswhose diameters D and G are 54 μm, and line widths of them are 1 μm. Itis desirable that the antenna coils are formed in global-routing layersin insulating resin over the chip of integrated circuit. Moreover, bothends of the coiled wirings of the antennas are opened and united withcapacitances whose values are denoted by min, which is C1 for thetransmitter antenna 1 and which is C2 for the receiver antenna 2.Moreover, an inductive electric power transfer circuit can be composedthat supply electric power to a chip of a integrated circuit withoutline from a substrate on which the chip of the integrated circuit ismounted; where a copper-wiring transmitter antenna 1 is formed in atrace layer of the substrate, and a coiled-copper-wiring receiverantenna 2 is formed in a trace layer in the chip of the integratedcircuit. Both axes of the coils are separated only in the direction ofX-axis by distance d of 7 μm, and are at a same position in thedirection of Y-axis. The coil of the transmitter antenna 1 and the coilof the receiver antenna 2 are placed in parallel with spacing h betweenantennas as shown in FIG. 18B.

FIG. 19A shows a graph for induced resistance r in this case at resonantfrequency f=140 GHz, resistance which is represented by non-dimensionalparameter r/(2πfL), as a function of spacing h between antennas, whichis represented by non-dimensional parameter (h/D). Effectiveself-inductances L of the coiled antennas are 1.3 nH. The coiledantennas have parasitic capacitance, min, of almost 0.001 pF betweenboth ends of the antennas, respectively. In FIG. 19A, the black circledenotes simulation, and the dotted line denotes (2/π) times the valuecalculated using approximate Equation 13. The graph of black circles,which show simulation, agrees with the graph of the dotted line as thegraph for the fourth embodiment does. When spacing h between antennas isalmost 10 μm, which is almost 20% of the coil diameter D(h/D=0.2),r/(2πfL) is almost 0.12, where induced resistance r is almost 140Ω. Whenspacing h between antennas is almost 20 μm, which is almost 40% of thecoil diameter D(h/D=0.4), r/(2πfL) is almost 0.08, where inducedresistance r is almost 90Ω. The impedance of the power supply circuit 3and load circuit 4 are matched to these induced resistances. FIG. 19Bshows power transfer efficiency from the power supply circuit 3 to theload circuit 4 as a function of spacing h between antennas, which isrepresented by non-dimensional parameter (h/D). FIG. 19B shows thatpower transfer efficiency is almost 80% when spacing h between antennasis almost 10 μm, which is almost 20% of coil diameter D(h/D=0.2),transferring the power efficiently. When the spacing h between antennasis almost 20 μm, which is almost 40% of coil diameter D(h/D=0.4), thepower transfer efficiency is almost 60%. By applying this effect, thesemiconductor integrated circuit can be composed with a transmitterantenna 1 and a receiver antenna 2 which are coiled wirings of 54 mm indiameter, which are separated by spacing h between antennas that is from10 μm to 20 μm, and which are faced each other. The circuit transferspower efficiently without power lines. Moreover, when spacing h betweenantennas, spacing which is spacing between layers for signal wiring andpower transfers through which, is enlarged by several times, similarlyenlarging diameters D of the antennas by several times, theinductive-electric-power-transfer circuit can transfer powerefficiently. Furthermore, as shown in FIG. 23, a circuit can be composedwith a chip of integrated circuit, which has a receiver antenna 2 in atrace layer, on a substrate, which has a copper transmitter antenna 1 ina trace layer, where the transmitter antenna 1 in the substrate islarger than the receiver antenna 2 in the integrated circuit.

Seventh Embodiment

An inductive electric power supply circuit according to a seventhembodiment is composed with: a transmitter antenna 1 which is almost 300mm in diameter and is connected with a power supply circuit 3; areceiver antenna 2 which is almost 300 mm in diameter and is in anelectric display device. Electric power is transferred from thetransmitter antenna 1 to the receiver antenna 2 through space; thereceiver antenna 2 is connected with a load circuit 4 of the electricdisplay device to work the device. This inductive electric powertransfer circuit works at the third type resonance of the principle ofthe present invention. In the seventh embodiment, electric power istransferred from the transmitter antenna 1 to the receiver antenna 2,which are three-turn-coiled copper wiring and face each other. Theantennas are almost 300 mm in diameter, which is six times that in FIG.14A for the third embodiment. The wirings of the antennas are 10 mm inwidth and 50 μm in thickness. These antenna wirings can be formed withetched-copper foil of 50 μm in thickness laminated on polyimide film.Effective self-inductances L1 and L2 of these coiled antennas are 4.9μH. Capacitances C1 and C2 of 100 pF connect both ends of coiled wiringsof the antennas, respectively. In this case, resonant frequency fbecomes 7.3 MHz. When spacing h between the transmitter antenna 1 andthe receiver antenna 2 becomes 300 mm which is even with diameters D ofthe antennas, coefficient of coupling k between the antennas becomesalmost 0.02, and induced resistances r1 and r2 become almost 4Ω. Powertransfer efficiency Pe in the matched circuit becomes almost 94%,thereby efficiently transferring the electric power.

The cause why the power transfer efficiency Pe becomes high is that,enlarging the antennas, resonant frequency f becomes low so that losscaused by skin effect in the wirings of the antennas becomes less. Thus,with large antennas, power can be efficiently transferred to an electricdisplay device through spacing h between the transmitter antenna 1 andthe receiver antenna 2 even though the spacing h is great.

(Modification 6)

An inductive electric power transfer circuit according to modification 6has large antennas of 300 mm in diameter, and supplies electric power toa vehicle which consumes the electric power. That is, an inductiveelectric power transfer circuit according to modification 6 has a powersupply circuit 3 in a power supply facility supplying electric powerwith electric current of frequency almost 7.3 MHz. The current is ledinto the transmitter antenna 1 that is a three-turned coil with diameterD of 300 mm square, and with line width of 10 mm. The power istransferred through spacing of 300 mm from the transmitter antenna 1 tothe receiver antenna 2 in a vehicle facing the transmitter antenna 1 inthe efficiency of almost 94%. The receiver antenna 2 transfers the powerto a load circuit 4 such as a battery in the vehicle.

Eighth Embodiment

An inductive electric power transfer circuit according to an eighthembodiment transfers power to electronics facility such as mobile phoneswithout power lines; the circuit has a transmitter antenna 1 and areceiver antenna 2 placed in coplanar as shown in the plan view of FIG.20A. That is, the inductive electric power transfer circuit has 47 mmsquare antennas, which are a transmitter antenna 1 and a receiverantenna 2 separated by 20 mm and placed on a flat-plane. This inductiveelectric power transfer circuit works in the third type resonance of theprinciple of the present invention. Coefficient of coupling k betweenthese antennas is 0.013. The transmitter antenna 1 and the receiverantenna 2 are coils which have two seven-turned wirings in two parallellevels that are parallel to XY-plane and separated each other by a gapof 1 mm. The shapes of the wirings in the two levels are formed so thattheir shadows projected into XY-pane are symmetric about Y-axis. Bothends of each antenna are not closed, and capacitances C1 and C2 areparasitic capacitance between both ends of their antennas, the parasiticcapacitances are represented by “min”. A terminal of power supplycircuit 3, port 1 (P1), is set in the middle of the wiring of thetransmitter antenna 1. A terminal of load circuit 4, port 2 (P2), is setin the middle of the wiring of the receiver antenna 2. When greatcapacitances are connected between both ends of the antennas, effectiveself-inductances L of the antennas are 8.9 μH. However, the effectiveinductances L of the antennas vary according to distribution of electriccurrent on the antennas. When both ends of each antenna are not closed,effective inductance of the antenna L is less than that of an antennawith great capacitance between both ends of the antenna. The antennasresonate at frequency f=23.8 MHz. Parasitic capacitances which arerepresented by “min” between both ends of the antennas are almost 5 pF,which are calculated assuming that the antennas have self-inductances of8.9 μH. When gap between the levels for wirings of an antenna is widen,the parasitic capacitance “min” becomes less.

Induced resistances r of the antennas in FIG. 20A are r=r1=r2=7Ω.Effective self-inductances L, which are used in approximate Equation 36,of the antennas are 3.6 μH, which is almost 40% of 8.9 μH of inductancesof the antennas of which great capacitances are connected between bothends. The cause why the effective self-inductances of the antennasgreatly change is that the parasitic capacitance “min” between twowirings that are facing each other in an antenna is enough to reduceeffective self-inductances of the antenna. FIG. 20B shows a graph forS21 of power transfer from the transmitter antenna 1 to the receiverantenna 2 as a function of frequency f. When impedances Z match withinduced resistances r, power is transferred efficiently as S21 is −0.73dB in which efficiency of power transfer is almost 85%. Thus, there isenough efficiency of power transfer even though the antennas areseparated in coplanar like this and coefficient of coupling k ofelectromagnetic induction between antennas is small as 0.013. On theother hand, the power transfer efficiency Pe is calculated as Pe=0.85using Equation 29 by substituting r1=7Ω and ref1=ref2=0.62Ω, whereeffective resistances ref1 and ref2 of a transmitter antenna 1 and areceiver antenna 2 are calculated accounting for skin effect. Thus, theEquation 29 gives the result which agrees with the result given from theelectromagnetic field simulation. An inductive electric power transfercircuit according to eighth embodiment has in coplanar plural coiledreceiver antennas 2, which are connected with plural electronic device,around a coiled transmitter antenna 1 on XY-plane. Therefore, theinductive power transfer circuit can supply power parallel to pluralelectronic devices through the receiver antennas. When the pluralreceiver antennas 2 are set up around the transmitter antenna 1,Z1/(2πfL1), which represents output impedance Z1 of a power supplycircuit 3 connected in series with the transmitter antenna 1, isadjusted to the sum of induced resistances r1 of the plural receiverantennas 2.

(Modification 7)

An inductive electric power transfer circuit according to modification 7has antennas that respectively have two seven-turned wirings on twoparallel planes separated by 4 mm, which is four times the separationaccording to the eighth embodiment. This model resonates at 40.1 MHz asa result of electromagnetic field simulation. Parasitic capacitances“min” between both ends of the antennas are calculated as 2 pF, which is40% of the parasitic capacitances according to eighth embodiment, whenusing effective self-inductances 8 μH that are given when both ends ofthe respective antennas are connected by great capacitances. Inducedresistances of the antennas r are r=r1=r2=18Ω. When the impedances Z arematched with the induced resistances r, power is transmitted in S21 of−0.455 dB, so that power is transferred in the efficiency of almost 90%,which is better than the efficiency of the previous example. Effectiveself-inductances L of the antennas to use in approximate Equation 36 are5.5 μH, which is almost 70% of 8 μH of inductances of antennas whoseboth ends are connected by great capacitances. Moreover, when spacingbetween the respective levels of the seven-turned wirings of thetransmitter antenna 1 and the receiver antenna 2 become wider into 8 mm,the antennas resonate at 51.4 MHz, the induced resistances r becomer=r1=r2=34Ω, and S21 becomes −0.32 dB, where power is transferred in theefficiency of almost 93%.

(Modification 8)

An inductive electric power transfer circuit according to modification 8has antennas which are one-layered seven-turned antennas which are halfof the antennas in FIG. 20A. The antennas are placed in coplanaralignment and separated 20 mm in distance as in FIG. 20A.

A power supply circuit 3 has terminals of port 1 (P1) connecting in themiddle of the wiring of the transmitter antenna 1 and a load circuit 4has terminals of port 2 (P2) connecting in the middle of the wiring ofthe receiver antenna 2. These components compose a model forelectromagnetic field simulation. The antennas according to modification8 have self-inductances L of 2.3 μH and have parasitic capacitances“min” of 0.8 pF between both ends of the antennas, respectively. Theantennas resonate at a frequency of 115 MHz. When the impedances Z ofthe circuits are matched to the induced resistances r concerned, theantennas in the alignment of FIG. 20A have the induced-resistances ofr=r1=r2=14Ω. S21 of power transfer between the antennas is −0.49 dB andpower is transferred in the efficiency of almost 89%.

Ninth Embodiment

An induced electric power transfer circuit according to ninth embodimenthas a transformer connected to a transmitter circuit 3 b or atransformer connected to a receiver circuit 4 b in FIG. 2B or has bothtransformers. The transformers have primary windings connected toterminals of ports in the antennas and secondary windings connected toterminals of the power supply circuit 3 or the load circuit 4. Theinduced electric power transfer circuit works at the third typeresonance of the principle of the present invention. In addition, asshown in FIG. 21A, the receiver antenna 2, which has capacitance C2between both ends of the antenna, according to this embodiment works asthe primary winding of the transformer. An inductive coupling wiring 6is a secondary wiring of the transformer, whose both ends are connectedto the load circuit 4 at port 4 (P4). Input impedance of the loadcircuit 4 is represented by the symbol Z4. The ninth embodiment isdescribed by FIG. 21 as follows. FIG. 21A is a plan view of atransmitter antenna 1, a receiver antenna 2, and an inductive couplingwiring 6 according to the ninth embodiment. The plan view in FIG. 21Ashows a transmitter antenna 1 and a receiver antenna 2 according toninth embodiment. The transmitter antenna 1 and the receiver antenna 2have shapes shown in FIG. 20A. They and the spiral inductive couplingwiring 6 are placed in coplanar on XY-plane. The spiral inductivecoupling wiring 6 is set in the center of the spiral wiring of thereceiver antenna 2. That is, the transmitter antenna 1 and the receiverantenna 2 in the inductive electric power transfer circuit is 47 mm insquare. They are placed in coplanar on XY-plane and separated by 20 mm.The antennas are coupled with mutual inductance M. The receiver antennaencircles the looped inductive coupling wiring 6, which is copperwiring, 5 μm in thickness, 1 mm in line width, and is from 10 mm through15 mm in diameter. Both ends of the inductive coupling wiring 6 areconnected to the terminals at port 4 (P4) in the load circuit 4.

When the inductive coupling wiring 6 is a looped wiring of 10 mm insquare and impedance Z4 of the load circuit 4 is 4Ω, electric power ismost efficiently transferred from the power supply circuit 3 to the loadcircuit 4. On the other hand, when the size of the loop of the inductivecoupling wiring 6 is enlarged into 15 mm in square; mutual inductance M2between the inductive coupling wiring 6 and the receiver antenna 2becomes greater, the impedance Z4 of the load circuit which matches toinduced resistance r3 of the inductive coupling wiring 6 grows into 20Ω.FIG. 21B shows a graph for power transfer efficiency Pe, which isrepresented by S41, as a function of frequency when the inductivecoupling wiring 6 has diameter of 10 mm to 15 mm. The graph shows poweris transferred efficiently. FIG. 21A shows that self-inductance of theinductive coupling wiring 6 is less comparable with induced resistancer2=7Ω generated in the receiver antenna 2. Therefore, the inputimpedance Z4 of the load circuit 4, which is connected with theinductive coupling wiring 6 at port 4 (P4), is set as follows totransfer electric power most efficiently from the power supply circuit 3to the load circuit. The adequate input impedance Z4 of the load circuit4 is (2πf×M2)²/r2=(M2/M)²×Z1, where M2 is mutual inductance between theinductive coupling wiring 6 and the receiver antenna 2. The receiverantenna 2 can work as the inductive coupling wiring 6, and both ends ofthe receiver antenna 2 can be connected to the load circuit 4 at port 4(P4). In that case, the power can be transferred most efficiently frompower supply circuit 3 to load circuit 4 when Z4 is (L2/M)²×Z1.

Moreover, the inductive electric power transfer circuit can have also atransmitter circuit 3 b in the left of FIG. 2B for a combination of atransmitter antenna 1 and a power supply circuit 3; the transmittercircuit 3 b has an inductive coupling wiring 6 that is inductivelycoupled with the transmitter antenna 1 by mutual inductance M1 and bothends of that are connected to the power supply circuit 3 at port 3 (P3).On the other hand, a receiver circuit 4 a in the right of FIG. 1A isused for receiver antenna 2. In that case, the output impedance Z3 ofthe power supply circuit 3 is converted into an induced resistance r2seen from the load circuit 4 at port 2 (P2) in the receiver antenna 2,the induced resistance r2 becomes almost (M/M1)²×Z3. Moreover, theinductive coupling wiring 6 also can work as a transmitter antenna 1. Inthat case, the output impedance Z3 of the power supply circuit 3 isconverted into an induced resistance r2 seen from the load circuit 4 atport 2 (P2) in the receiver antenna 2, the induced resistance r2 becomesalmost (M/L1)²×Z3.

Tenth Embodiment

An inductive electric power transfer circuit according to a tenthembodiment is an impedance converter 5 that has air-core coil and usesthe first type resonance of the present invention. That is, it is acircuit of FIG. 2A in which L1×C1=L2×C2=1/ωo² and angular frequency ω ofthe current transferring power is ω0; when output impedance Z1 of apower supply circuit 3, which is connected in series with a transferantenna 1 at port 1 (P1), is set to r1=αωM, input impedance Z2 of a loadcircuit 4, which is connected in series with a receiver antenna 2 atport 2 (P2), becomes r2=ωM/α, where α is arbitrary positive parameter.Thus, the inductive electric power transfer circuit to convert impedanceand to transfer power from the power supply circuit 3 to the loadcircuit 4 can be composed. That is, an impedance converter 5 iscomposed, which can arbitrarily change ratio between impedances of thepower supply circuit 3 and the load circuit 4 keeping constant productof both impedances.

The impedance converter 5 according to the tenth embodiment has the samefunction as impedance converter with transmission line of quarterwavelength of the electromagnetic field. Although an impedance converterwith transmission line of quarter wavelength should form the length ofthe wiring for the transmission line, the impedance converter 5according to the tenth embodiment can be smaller than quarter wavelengthof the electromagnetic field by connecting capacitances C1 and C2between both ends of the transmitter antenna 1 and the receiver antenna2, respectively. Moreover, an impedance converter consisting ofquarter-wavelength transmission line is difficult to use because theconverter converts impedance from Z_(o)×α to Z_(o)/α, where Z_(o) isfixed basic impedance for impedance conversion as the characteristicimpedance of the transmission line, though a is arbitrary changeablepositive parameter. On the other hand, the impedance converter 5according to tenth embodiment is easy to use because the converter useschangeable basic impedance ωM for impedance conversion, where M ismutual inductance changeable by changing distance between thetransmission antenna 1 and the receiver antenna 2.

In tenth embodiment, induced resistance r2 is generated on the coiledreceiver antenna 2 by the electromagnetic field generated from thetransmitter antenna 1. Electric power can be efficiently transferred toreceiver antenna 2 by connecting load circuit 4 with input impedancematched with the induced resistance r2. Induced voltage on the receiverantenna 2 is proportional to the magnetic field in the area of receiverantenna 2 caused by transmitter antenna 1. When the magnetic field isreduced, the induced voltage on the receiver antenna 2 is reduced. Inthat case, when input impedance of the load circuit 4 decreases, circuitwhich is connected with the receiver antenna 2, electric current I2,which is on the receiver antenna 2, increases and the receiver antenna 2receives greater electric power. When conductor loss of the receiverantenna 2 decreases, the current I2 on the receiver antenna 2 increasesto the extent that power transfer efficiency from the transmitterantenna 1 to the receiver antenna 2 is almost 100%. When the current I2increases on the receiver antenna 2, induced resistance r1 on thetransmitter antenna 1, which is caused by the current I2, increases toforce the transmitter antenna 1 supply more power. Thus, power can betransferred with almost 100% efficiency from the power supply circuit 3,which is connected to the transmitter antenna 1, to the load circuit 4,which is connected to the receiver antenna 2.

An inductive electric power transfer circuit can be used wherecoefficient of coupling k between the transmitter antenna 1 and thereceiver antenna 2 is not limited to greater than 0.004. For instance,the coefficient of coupling k between those antennas becomes smallerthan 0.004 for the inductive electric power transfer circuit thattransfers power from the transmitter antenna 1 out of human body to thereceiver antenna 2 in a capsular endoscope taken in a human body. Then,the mutual inductance M between the antennas becomes small according toEquation 23, thereby reducing the induced resistances r1 and r2according to Equations 33 and 34. Then, there is a problem that powertransfer efficiency Pe, which is according to Equation 29, becomesworse. In spite of that, the inductive electric power transfer circuitcan transfer power efficiently when it is set as follows. That is,current I1 on the transmitter antenna 1 is enlarged more than current I2on the receiver antenna 2 to reduce electric current ratio parameter α;the induced resistance r2 on the receiver antenna 2, which is calculatedusing Equation 34, becomes greater than effective resistance ref2 of thereceiver antenna 2, so that power transfer efficiency Pe, which iscalculated using Equation 29, is enlarged. Effective resistance ref1 ofthe transmitter antenna 1, which is out of human body, can be smallerthan induced resistance r1 by forming the antenna 1 with superconductor.With these methods, the inductive electric power transfer circuit canhave high power transfer efficiency Pe, which is calculated usingEquation 29.

(Modification 9)

An inductive electric power transfer circuit according to a transferredexample 9 has a combination of a load circuit 4 and a receiver antenna2, combination which is a receiver circuit 4 b of the right side of FIG.2B, so that the receiver antenna 2 is inductively coupled with ainductive coupling wiring 6 with mutual inductance M, and both ends ofthe inductive coupling wiring 6 are connected to a load circuit 4 atport 4. As shown precisely in FIG. 21A, the inductive coupling wiring 6is inductively coupled with the receiver antenna 2, and both ends of theinductive coupling wiring 6 are connected to the load circuit 4 at port4 (P4). On the other hand, the combination of a power supply circuit 3and a transmitter antenna 1 is composed of a transmitter circuit 3 a,which is a series circuit, in the left of FIG. 2A. The input impedanceof a load circuit 4 that is connected at port 4 is represented by thesymbol Z4. Output impedance Z1 of a power supply circuit 3 according tomodification 9 is converted into induced resistance of almost (M2/M)²×Z1opposite the load circuit 4. Power can be most efficiently transferredto the load circuit 4 when the induced resistance is matched with inputimpedance Z4 of the load circuit 4. Additionally, the receiver antenna2, which has effective self-inductance L2, can combine with theinductive coupling wiring 6 as shown in a receiver circuit 4 c of theleft of FIG. 2C, and a load circuit 4 and a capacitance C2 can beconnected in parallel between both ends of the receiver antenna 2 atport 6. In that case, output impedance Z1 of power supply circuit 3 isconverted into induced resistance of almost (L2/M)²×Z1 opposite the loadcircuit 4 at port 4. Power can be most efficiently transferred to theload circuit 4 when the induced resistance is matched with inputimpedance Z4 of the load circuit 4.

(Modification 10)

An inductive electric power transfer circuit according to a modification10 has a combination of a transmitter antenna 1 and a power supplycircuit 3 which is similar to the combination of a receiver antenna 2and a load circuit 4 that is composed as FIG. 21A, which is composed ofa transmitter antenna 1 and a inductive coupling wiring 6 that isinductively coupled with the transmitter antenna 1 and a power supplycircuit 3 that is connected between both ends of the inductive couplingwiring 6. The combination of a transmitter antenna 1 and a power supplycircuit according to modification 10 is a transmitter circuit 3 b in theleft of FIG. 2B, where the inductive coupling wiring 6 is inductivelycoupled with the transmitter antenna 1 with mutual inductance M1, andboth ends of the inductive coupling wiring 6 are connected to the powersupply circuit at port 3 (P3). Output impedance of the power supplycircuit 3 is represented by the symbol Z3. A combination of a receiverantenna 2 and a load circuit 4 is a series circuit of receiver circuit 4a in the right of FIG. 2A. The composition according to modification 10converts output impedance Z3 of the power supply circuit 3 into inducedresistance r2=(M/M1)²×Z3 seen from the load circuit 4. When inputimpedance Z2 of the load circuit 4 is matched to the induced resistancer2, power can be transferred most efficiently. On the other hand, aninductive electric power transfer circuit can have a transmitter antenna1, with effective self-inductance L1, that combines with a inductivecoupling wiring 6, the transmitter antenna 1 is in a transmitter circuit3 c in the left of FIG. 2C, where a power supply circuit 3 and acapacitance C1 are connected in parallel between both ends of thetransmitter antenna 1 at port 5. In that case, the output impedance Z3of the power supply circuit 3 is converted into induced resistancer2=(M/L1)²×Z3 seen from the load circuit 4. When the input impedance Z2of the load circuit 4 is matched to the induced resistance r2, power canbe transferred most efficiently.

Eleventh Embodiment

An inductive electric power transfer circuit according to an eleventhembodiment uses the impedance converter 5 of the tenth embodiment toadapt changes of impedance when distance between a transmitter antenna 1and a receiver antenna 2 changes. FIG. 22B shows a plan view of theinductive electric power transfer circuit according to the eleventhembodiment. Although FIG. 22B shows the case when the inductance L1 ofthe coiled transmitter antenna 1 is the same as the inductance L2 of thecoiled receiver antenna 2 as L=L1=L2, this embodiment can be applied tothe case when their impedances are different each other. FIG. 22A showsa plan view of an inductive electric power transfer circuit composed ofa transmitter antenna 1 and a receiver antenna 2 without impedanceconverter 5. Mo is defined as mutual inductance M between a transmitterantenna 1 and a receiver antenna 2 when inductive coupling coefficient kbetween them is k0. In that case in which the antennas resonate atangular frequency ω=ωo=1/√(L1·C1), when output impedance Z2 of the loadcircuit 4 is matched to ωMo according to Equations 30 and 31, power canbe transferred in full efficiency.

The circuit in FIG. 22B is described as follows. FIG. 22B shows aninductive electric power transfer circuit in which distance between atransmitter antenna 1 and a receiver antenna 2 changes and coefficientof coupling k between both antennas changes; the change is compensatedby the impedance converter 5 according to tenth embodiment, which isinserted between a power supply circuit 3 and a transmitter antenna 1 atport 1 (P1). That is, the power supply circuit 3, which has fixed outputimpedance Z1=ωoMo, is connected to an input terminal that is in themiddle of a transmitter antenna in the impedance converter 5; an outputterminal that is in the middle of a receiver antenna in the impedanceconverter 5 is connected to port 1 (P1) that is in the middle of thetransmitter antenna 1. This impedance converter 5 changes distancebetween its transmitter antenna and receiver antenna, or changesdistance between axes of coil of both antennas; so that mutualinductance between both antennas can be adjusted freely. When placementof the transmitter antenna 1 and the receiver antenna 2 changes and thedistance between the antennas becomes far, coefficient of coupling kbetween the transmitter antenna 1 and the receiver antenna 2 becomessmall and mutual inductance M becomes small. It is assumed that themutual inductance M becomes small as Mo/_(Y), where _(Y) is a realnumber parameter that is greater than one. In this case, input impedanceZ2, which is fixed to ωMo, of load circuit 4 that is connected to thereceiver antenna 2 at port 2(P2) is converted into impedance Z5=ωMo/_(Y)₂ at port 1 (P1) seen from the transmitter antenna 1. For this reason,the impedance converter 5 needs to convert output impedance Z1, which isfixed to ωMo, of the power supply circuit 3 into impedance Z5=ωMo/_(Y) ₂at port 1 (P1) seen from the transmitter antenna 1. To achieve this, theimpedance converter 5 changes mutual inductance between its transmitterantenna and receiver antenna into ωoMo/_(Y) by changing coefficient ofcoupling k between them by changing distance between them. As a result,the impedance from the power supply circuit 3 is converted into theimpedance that matches the impedance converted from the load circuit 4at port 1 (P1).

Thus, power can be transferred in full efficiency by matching impedancesfrom the power supply circuit 3 that has fixed output impedance Z1through the load circuit 4 that has fixed input impedance Z2 by theimpedance converter that compensates the change of the mutual inductancebetween the transmitter antenna 1 and the receiver antenna 2, in whichthe change is caused by change of their placement. As described above,the impedance converter 5 compensates the change of the impedance bymatching impedance when mutual impedance M between the transmitterantenna 1 and the receiver antenna 2 changes, by converting theimpedance properly and keeping resonant angular frequency ω to ωo, andby adjusting just one parameter of distance between antennas to changemutual inductance between them in the converter 5. An inductive electricpower transfer circuit according to this embodiment has merits that itis simple since it keeps resonance frequency constant, and it is easy toadjust impedance since it needs only one parameter for the adjustment.

Twelfth Embodiment

FIG. 23A shows an inductive electric power transfer circuit according toa twelfth embodiment. The circuit has a receiver antenna 2 whosediameter G is one-sixth of diameter D of a transmitter antenna 1. Thereceiver antenna 2 is placed in coplanar with, and in the middle of, thetransmitter antenna 1 on XY-plane. The transmitter antenna 1 is aone-turn loop of 300 mm square in diameter D, 1 mm in line width Thisinductive electric power transfer circuit works in the third typeresonance of the principle of the present invention. The receiverantenna 2 is 47 mm in diameter G, and has two seven-turned spiralwirings which are opposed each other on two levels. The spiral wiringsare connected at port 2 (P2) as in FIG. 20A of the eighth embodiment.Distance between the levels, vertical to XY-plane, is 1 mm. Acapacitance C1 of 116 pF composed of a capacitor (capacitance device) isconnected between both ends of the transmitter antenna 1. A capacitanceC2 composed of capacitor (capacitance device) of 15.6 pF and parasiticcapacitance of 5.2 pF is connected between ends of the receiver circuit.Self-inductance L1 of the transmitter antenna 1 is 1.5 μH, and effectiveself-inductance L2 of the receiver antenna 2 is 8.9 μH.

The transmitter antenna 1 and the receiver antenna 2 of the inductiveelectric power transfer circuit resonates at 12 MHz where angularfrequency ω is equal to ωo, which is the first type resonance of theprinciple of the present invention. The transmitter antenna 1 has aninduced resistance r1 of 3.3Ω, which is matched with output impedance ofthe power supply circuit 3 to transfer power. The receiver antenna 2 hasan induced resistance r2 of 4.3Ω, which is matched with input impedanceof the load circuit 4 to transfer power. However, these inducedresistances r1 and r2 can change according to Equations 33 and 34depending on ratio of resonant current I1 on the transmitter antenna 1and resonant current I2 on the receiver antenna 2 in the condition ofkeeping product of r1 and r2 constant. Coefficient of coupling k betweenthe transmitter antenna 1 and the receiver antenna 2 is calculated ask=√(r1·r2/(L1·L2))/(2πf)=0.014 by substituting the induced resistancesobtained from simulation.

FIG. 23B shows a graph for power transfer efficiency Pe, which isrepresented by S21 from the transmitter antenna 1 to the receiverantenna 2, as a function of frequency. S21 is −1.33 dB at a frequency of12 MHz. This means that power transfer efficiency Pe is almost 75% to beefficient. Thus, the inductive electric power transfer circuit cantransfer power efficiently although the receiver antenna 2 has thediameter of one-sixth of the diameter G of the transmitter antenna 1. Asto difference between resonant frequencies of both antennas due todifference of characteristics of parts in the inductive electric powertransfer circuit, the difference can be within the extent that iseffective to transfer power without obstacle, as described in the firstembodiment, when the coefficient of coupling k between the transmitterantenna 1 and the receiver antenna 2 is adjusted to 0.04 or more. Powercan be transferred efficiently by making the ratio of diameter of theantennas within 12, since coefficient of coupling k between the antennasis almost 0.04 when the diameter G of the receiver antenna 2 is almostone-twelfth of the diameter D of the transmitter antenna 1. Power can betransferred without obstacle practically like the modifications 2 and 4of the first embodiment when the distance between the centers of thecoils of the receiver antenna 2 and the transmitter antenna 1 is withintwice the diameter of the largest antenna.

Thirteenth Embodiment

An inductive electric power transfer circuit according to a thirteenthembodiment has an antenna that receives electromagnetic wave from theair, the antenna is substituted for a combination of a power supplycircuit and a transmitter antenna 1; or the circuit has an antenna thatradiates electromagnetic wave into the air, the antenna is substitutedfor a combination of a load circuit and a receiver antenna 2. Thecircuit according to this embodiment works in the first type resonanceof the principle of the present invention. The inductive electric powertransfer circuit in FIG. 24A has a copper dipole antenna of 1 mm inwidth, 940 mm in length in the direction of X-axis which is atransmitter antenna 1, which receives electromagnetic wave from the airand converts it into electric power. The function that receiveselectromagnetic wave and converts it into electric power is substitutedfor a power supply circuit 3. A receiver antenna 2 in FIG. 24A is acoiled copper wiring antenna with diameter G=54 mm in square that isformed on a polyimide film. The level of the receiver antenna 2 isseparated 10 mm from the level of the transmitter antenna 1 in thedirection vertical to XY-plane. The receiver antenna 2 is separated 1 mmfrom the transmitter antenna 1 in the direction of Y-axis. The receiverantenna 2 is a three-turned wiring coil that has a gap between both endsof the wiring coil without external capacitor between them and has port2 (P2) in the middle of the wiring coil like the wiring coil in FIG. 14according to the third embodiment. The inductive electric power transfercircuit has current I1 on the transmitter antenna 1 and current I2 onthe receiver antenna 2 with a phase difference of 90 degrees between thecurrents, cos (β) is zero, the resonant angular frequency ω is ωoaccording to Equations 33 through 35, and the antennas resonate at afrequency of 154 MHz. In one case, induced resistances r1 and r2 on thetransmitter antenna 1 and the receiver antenna 2 are 30Ω. The inducedresistances r1 and r2 change depending on the ratio of the current I1 onthe transmitter antenna 1 and the current I2 on the receiver antenna 2according to Equations 33 and 34, and product of r1 and r2 is keptconstant. The induced resistance r1 is equated with radiation resistanceof the transmitter antenna 1 since the radiation resistance is regardedas output impedance Z1 of a function of a power supply circuit 3generated on the antenna. The induced resistance r2 is settled accordingto the resistance r1. Then, the input impedance Z2 of load circuit 4 isadjusted to the resistance r2. Thus, the induced resistances r1 and r2are, for power transfer, matched with the output impedance Z1 of thepower supply circuit 3 and the input impedance Z2 of the load circuit 4.

FIG. 24B shows a graph for power transfer efficiency Pe, which isrepresented by S21 from the transmitter antenna 1 to the receiverantenna 2, as a function of frequency. At 154 MHz of a resonantfrequency f, power transfer efficiency Pe is almost 76% which is −1.21dB in S21. Thus, the inductive electric power transfer circuit, whichhas the dipole antenna of the transmitter antenna 1 and the coil of thereceiver antenna 2, can transfer power in good efficiency. For amodification, the width of the antenna wiring of the dipole antenna ofthe transmitter antenna 1 is widen nine times into almost 10 mm, so thateffective resistance ref1 of the antenna wiring becomes one-ninth.Effective resistance ref2 of the antenna wiring of the receiver antenna2 is not changed. The current I1 on the transmitter antenna 1 is set tothree times the current I2 on the receiver antenna 2, so that the ratioα between electric currents in Equations 33 and 34 becomes one-third, r1one-third, and r2 triples. Then, power transfer efficiency Pe accordingto Equation 29 rises, and loss rate of power (1−Pe) decreases intoalmost one-third. In the example where spacing h between the levels ofthe transmitter antenna 1 and the receiver antenna 2 is 2 mm which isreduced to one-fifth, then, power transfer efficiency Pe according tothe embodiment can be almost 86%, the induced resistances are r1=r2=40Ω,and S21 is −0.63 dB. The inductive electric power transfer circuitaccording to the embodiment has the dipole antenna that receiveselectromagnetic wave from the air and supplies its power to the circuit;the antenna is substituted for a combination of a power supply circuit 3and a transmitter antenna 1. The circuit transfers power as efficientlyas previous embodiments.

For another modification, an inductive electric power transfer circuitis constructed as the combination of a transmitter antenna 1 and a powersupply circuit 3 is exchanged for the combination of a receiver circuit2 and a load circuit 4. That is, the inductive electric power transfercircuit has a dipole antenna as a combination of a receiver antenna 2and a load circuit 4, the dipole antenna radiates electromagnetic waveinto the air to consume power as a function of a load circuit 4.

For another example, the antenna system according to the embodiment canreduce the size by one digit having metal patterns on a flexiblesubstrate such as a polyimide film. The system has a dipole antenna or aspiral dipole antenna that receives electromagnetic wave from the air asa combination of a power supply circuit 3 and a transmitter antenna 1.The system has a receiver antenna 2 close to the transmitter antenna 1.The receiver antenna 2 is a three-turned metal spiral of 5 mm in squareon a resin, or ceramic, substrate of 6 mm in square. And both ends ofthe receiver antenna 2 are not closed. The inductive electric powertransfer circuit has the receiver circuit 4 in an IC-chip connected, inseries with, in the middle of the receiver antenna 2 at port 2 (P2).Since the antennas are reduced in size by one digit, resonant frequencybecomes almost 1.5 GHz. However, the induced resistance r is almost sameas that in the former example. For another example, the resonantfrequency can be reduced by increasing the number of turns of theantennas or connecting an external capacitor of great capacitancebetween both ends of the antennas.

INDUSTRIAL APPLICABILITY

The inductive electric power transfer circuits according to the presentinvention are applicable for supplying power through space from powersupply facilities to vehicles etc. Moreover, they are applicable forsupplying power through a wall of houses to display units etc. Moreover,they are applicable for supplying power to in vivo electronic devicesburied in human body through the skin without power lines. Moreover,they are applicable for transferring power between tracing layers insemiconductor integrated circuits without power line. Moreover, they areapplicable for transferring power between an antenna and an electronicdevice through space; the antenna receives or radiates electromagneticwave from or into the air; the antenna has a function of a power supplycircuit and transmitter antenna, or a function of a load circuit and areceiver circuit.

1. An inductive electric power transfer circuit, comprising: atransmitter antenna connected with a series power supply circuit thatsupply electric power at angular frequency ω; a receiver antennaconnected with a series load circuit that consume the electric power;capacitance C1 which is connected between both ends of the transmitterantenna; and capacitance C2 which is connected between both ends of thereceiver antenna; wherein distance between the transmitter antenna andthe receiver antenna is not greater than ½/2π wavelengths ofelectromagnetic field at the angular frequency ω, the transmitterantenna has effective self-inductance L1, and the receiver antenna haseffective self-inductance L2, the magnetic inductive coupling factorbetween the transmitter antenna and the receiver antenna is representedby the symbol k, and wherein with a phase angle β that is not less thanzero and not greater than pi, the angular frequency ω is reciprocal ofsquare root of L2×C2×(1+k×cos (β)), the power supply circuit has outputimpedance of k ωL1×sin (β)≡r1, and the load circuit has input impedanceof kωL2×sin (β)≡r2, thereby efficiently transferring power from thepower supply circuit to the load circuit through space.
 2. The inductiveelectric power transfer circuit according to claim 1, wherein thecombination of the transmitter antenna and the power supply circuit isreplaced with a combination of a second transmitter antenna and a firstinductive coupling wiring and a second power supply circuit, both endsof the first inductive coupling wiring are connected with the secondpower supply circuit, mutual inductance between the second transmitterantenna and the first inductive coupling wiring are represented by thesymbol M1, and output impedance of the second power supply circuit is(2πf×M1)²/r1.
 3. The inductive electric power transfer circuit accordingto claim 1, wherein the combination of the receiver antenna and the loadcircuit is replaced with a combination of a second receiver antenna anda second inductive coupling wiring and a second load circuit, both endsof the second inductive coupling wiring are connected with the secondload circuit, mutual inductance between the second receiver antenna andthe second inductive coupling wiring is represented by the symbol M2,and input impedance of the second load circuit is (2πf×M2)²/r2.
 4. Theinductive electric power transfer circuit according to claim 1, whereinthe combination of the transmitter antenna and the capacitance C1 andthe power supply circuit is replaced with an antenna that receiveelectromagnetic wave from the air.
 5. The inductive electric powertransfer circuit according to claim 1, wherein the combination of thereceiver antenna and the capacitance C2 and the load circuit is replacedwith an antenna that radiate electromagnetic wave into the air.
 6. Theinductive electric power transfer circuit according to claim 2, whereinthe second transmitter antenna combines the first inductive couplingwiring, and output impedance of the second power supply circuit is(2πf×L1)²/r1.
 7. The inductive electric power transfer circuit accordingto claim 3, wherein the second receiver antenna combines the secondinductive coupling wiring, and input impedance of the second loadcircuit is (2πf×L2)²/r2.
 8. An inductive electric power transfercircuit, comprising: a transmitter antenna connected with a series powersupply circuit that supply electric power at angular frequency ω; areceiver antenna connected with a series load circuit that consume theelectric power; capacitance C1 which is connected between both ends ofthe transmitter antenna; and capacitance C2 which is connected betweenboth ends of the receiver antenna; wherein distance between thetransmitter antenna and the receiver antenna is not greater than ½πwavelengths of electromagnetic field at the angular frequency ω, thetransmitter antenna has effective self-inductance L1, the receiverantenna has effective self-inductance L2, the mutual inductance betweenthe transmitter antenna and the receiver antenna is represented by thesymbol M, and output impedance of the power supply circuit isrepresented by the symbol Z1, and wherein the angular frequency ω isreciprocal of square root of L2×C2, and the load circuit has inputimpedance of (ωM)²/Z1, thereby efficiently transferring power from thepower supply circuit to the load circuit through space.
 9. The inductiveelectric power transfer circuit according to claim 8, wherein thecombination of the transmitter antenna and the power supply circuit isreplaced with a combination of a second transmitter antenna and a firstinductive coupling wiring and a second power supply circuit, both endsof the first inductive coupling wiring are connected with the secondpower supply circuit, mutual inductance between the second transmitterantenna and the first inductive coupling wiring are represented by thesymbol M1, output impedance of the second power supply circuit isrepresented by the symbol Z3, and input impedance of the load circuit is(M/M1)²Z3.
 10. The inductive electric power transfer circuit accordingto claim 8, wherein the combination of the receiver antenna and the loadcircuit is replaced with a combination of a second receiver antenna anda second inductive coupling wiring and a second load circuit, both endsof the second inductive coupling wiring are connected with the secondload circuit, mutual inductance between the second receiver antenna andthe second inductive coupling wiring are represented by the symbol M2,and input impedance of the second load circuit is (M2/M)²Z1.
 11. Theinductive electric power transfer circuit according to claim 9, whereinthe second transmitter antenna combines the first inductive couplingwiring, and input impedance of the load circuit is (M/L1)²Z3.
 12. Theinductive electric power transfer circuit according to claim 10, whereinthe second receiver antenna combines the second inductive couplingwiring, and input impedance of the second load circuit is (L2/M)²Z1.